diff options
Diffstat (limited to 'Documentation')
25 files changed, 504 insertions, 218 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb index a07c0f366f9..a986e9bbba3 100644 --- a/Documentation/ABI/testing/sysfs-bus-usb +++ b/Documentation/ABI/testing/sysfs-bus-usb @@ -159,3 +159,14 @@ Description: device. This is useful to ensure auto probing won't match the driver to the device. For example: # echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id + +What: /sys/bus/usb/device/.../avoid_reset +Date: December 2009 +Contact: Oliver Neukum <oliver@neukum.org> +Description: + Writing 1 to this file tells the kernel that this + device will morph into another mode when it is reset. + Drivers will not use reset for error handling for + such devices. +Users: + usb_modeswitch diff --git a/Documentation/ABI/testing/sysfs-platform-asus-laptop b/Documentation/ABI/testing/sysfs-platform-asus-laptop index a1cb660c50c..1d775390e85 100644 --- a/Documentation/ABI/testing/sysfs-platform-asus-laptop +++ b/Documentation/ABI/testing/sysfs-platform-asus-laptop @@ -1,4 +1,4 @@ -What: /sys/devices/platform/asus-laptop/display +What: /sys/devices/platform/asus_laptop/display Date: January 2007 KernelVersion: 2.6.20 Contact: "Corentin Chary" <corentincj@iksaif.net> @@ -13,7 +13,7 @@ Description: Ex: - 0 (0000b) means no display - 3 (0011b) CRT+LCD. -What: /sys/devices/platform/asus-laptop/gps +What: /sys/devices/platform/asus_laptop/gps Date: January 2007 KernelVersion: 2.6.20 Contact: "Corentin Chary" <corentincj@iksaif.net> @@ -21,7 +21,7 @@ Description: Control the gps device. 1 means on, 0 means off. Users: Lapsus -What: /sys/devices/platform/asus-laptop/ledd +What: /sys/devices/platform/asus_laptop/ledd Date: January 2007 KernelVersion: 2.6.20 Contact: "Corentin Chary" <corentincj@iksaif.net> @@ -29,11 +29,11 @@ Description: Some models like the W1N have a LED display that can be used to display several informations. To control the LED display, use the following : - echo 0x0T000DDD > /sys/devices/platform/asus-laptop/ + echo 0x0T000DDD > /sys/devices/platform/asus_laptop/ where T control the 3 letters display, and DDD the 3 digits display. The DDD table can be found in Documentation/laptops/asus-laptop.txt -What: /sys/devices/platform/asus-laptop/bluetooth +What: /sys/devices/platform/asus_laptop/bluetooth Date: January 2007 KernelVersion: 2.6.20 Contact: "Corentin Chary" <corentincj@iksaif.net> @@ -42,7 +42,7 @@ Description: This may control the led, the device or both. Users: Lapsus -What: /sys/devices/platform/asus-laptop/wlan +What: /sys/devices/platform/asus_laptop/wlan Date: January 2007 KernelVersion: 2.6.20 Contact: "Corentin Chary" <corentincj@iksaif.net> diff --git a/Documentation/ABI/testing/sysfs-platform-eeepc-laptop b/Documentation/ABI/testing/sysfs-platform-eeepc-laptop index 7445dfb321b..5b026c69587 100644 --- a/Documentation/ABI/testing/sysfs-platform-eeepc-laptop +++ b/Documentation/ABI/testing/sysfs-platform-eeepc-laptop @@ -1,4 +1,4 @@ -What: /sys/devices/platform/eeepc-laptop/disp +What: /sys/devices/platform/eeepc/disp Date: May 2008 KernelVersion: 2.6.26 Contact: "Corentin Chary" <corentincj@iksaif.net> @@ -9,21 +9,21 @@ Description: - 3 = LCD+CRT If you run X11, you should use xrandr instead. -What: /sys/devices/platform/eeepc-laptop/camera +What: /sys/devices/platform/eeepc/camera Date: May 2008 KernelVersion: 2.6.26 Contact: "Corentin Chary" <corentincj@iksaif.net> Description: Control the camera. 1 means on, 0 means off. -What: /sys/devices/platform/eeepc-laptop/cardr +What: /sys/devices/platform/eeepc/cardr Date: May 2008 KernelVersion: 2.6.26 Contact: "Corentin Chary" <corentincj@iksaif.net> Description: Control the card reader. 1 means on, 0 means off. -What: /sys/devices/platform/eeepc-laptop/cpufv +What: /sys/devices/platform/eeepc/cpufv Date: Jun 2009 KernelVersion: 2.6.31 Contact: "Corentin Chary" <corentincj@iksaif.net> @@ -42,7 +42,7 @@ Description: `------------ Availables modes For example, 0x301 means: mode 1 selected, 3 available modes. -What: /sys/devices/platform/eeepc-laptop/available_cpufv +What: /sys/devices/platform/eeepc/available_cpufv Date: Jun 2009 KernelVersion: 2.6.31 Contact: "Corentin Chary" <corentincj@iksaif.net> diff --git a/Documentation/DocBook/device-drivers.tmpl b/Documentation/DocBook/device-drivers.tmpl index f9a6e2c75f1..1b2dd4fc3db 100644 --- a/Documentation/DocBook/device-drivers.tmpl +++ b/Documentation/DocBook/device-drivers.tmpl @@ -45,7 +45,7 @@ </sect1> <sect1><title>Atomic and pointer manipulation</title> -!Iarch/x86/include/asm/atomic_32.h +!Iarch/x86/include/asm/atomic.h !Iarch/x86/include/asm/unaligned.h </sect1> diff --git a/Documentation/DocBook/deviceiobook.tmpl b/Documentation/DocBook/deviceiobook.tmpl index 3ed88126ab8..c1ed6a49e59 100644 --- a/Documentation/DocBook/deviceiobook.tmpl +++ b/Documentation/DocBook/deviceiobook.tmpl @@ -316,7 +316,7 @@ CPU B: spin_unlock_irqrestore(&dev_lock, flags) <chapter id="pubfunctions"> <title>Public Functions Provided</title> -!Iarch/x86/include/asm/io_32.h +!Iarch/x86/include/asm/io.h !Elib/iomap.c </chapter> diff --git a/Documentation/cdrom/ide-cd b/Documentation/cdrom/ide-cd index 2c558cd6c1e..f4dc9de2694 100644 --- a/Documentation/cdrom/ide-cd +++ b/Documentation/cdrom/ide-cd @@ -159,42 +159,7 @@ two arguments: the CDROM device, and the slot number to which you wish to change. If the slot number is -1, the drive is unloaded. -4. Compilation options ----------------------- - -There are a few additional options which can be set when compiling the -driver. Most people should not need to mess with any of these; they -are listed here simply for completeness. A compilation option can be -enabled by adding a line of the form `#define <option> 1' to the top -of ide-cd.c. All these options are disabled by default. - -VERBOSE_IDE_CD_ERRORS - If this is set, ATAPI error codes will be translated into textual - descriptions. In addition, a dump is made of the command which - provoked the error. This is off by default to save the memory used - by the (somewhat long) table of error descriptions. - -STANDARD_ATAPI - If this is set, the code needed to deal with certain drives which do - not properly implement the ATAPI spec will be disabled. If you know - your drive implements ATAPI properly, you can turn this on to get a - slightly smaller kernel. - -NO_DOOR_LOCKING - If this is set, the driver will never attempt to lock the door of - the drive. - -CDROM_NBLOCKS_BUFFER - This sets the size of the buffer to be used for a CDROMREADAUDIO - ioctl. The default is 8. - -TEST - This currently enables an additional ioctl which enables a user-mode - program to execute an arbitrary packet command. See the source for - details. This should be left off unless you know what you're doing. - - -5. Common problems +4. Common problems ------------------ This section discusses some common problems encountered when trying to @@ -371,7 +336,7 @@ f. Data corruption. expense of low system performance. -6. cdchange.c +5. cdchange.c ------------- /* diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt index 73ef30dbe61..31575e220f3 100644 --- a/Documentation/feature-removal-schedule.txt +++ b/Documentation/feature-removal-schedule.txt @@ -117,19 +117,25 @@ Who: Mauro Carvalho Chehab <mchehab@infradead.org> --------------------------- What: PCMCIA control ioctl (needed for pcmcia-cs [cardmgr, cardctl]) -When: November 2005 +When: 2.6.35/2.6.36 Files: drivers/pcmcia/: pcmcia_ioctl.c Why: With the 16-bit PCMCIA subsystem now behaving (almost) like a normal hotpluggable bus, and with it using the default kernel infrastructure (hotplug, driver core, sysfs) keeping the PCMCIA control ioctl needed by cardmgr and cardctl from pcmcia-cs is - unnecessary, and makes further cleanups and integration of the + unnecessary and potentially harmful (it does not provide for + proper locking), and makes further cleanups and integration of the PCMCIA subsystem into the Linux kernel device driver model more difficult. The features provided by cardmgr and cardctl are either handled by the kernel itself now or are available in the new pcmciautils package available at http://kernel.org/pub/linux/utils/kernel/pcmcia/ -Who: Dominik Brodowski <linux@brodo.de> + + For all architectures except ARM, the associated config symbol + has been removed from kernel 2.6.34; for ARM, it will be likely + be removed from kernel 2.6.35. The actual code will then likely + be removed from kernel 2.6.36. +Who: Dominik Brodowski <linux@dominikbrodowski.net> --------------------------- @@ -550,3 +556,35 @@ Why: udev fully replaces this special file system that only contains CAPI NCCI TTY device nodes. User space (pppdcapiplugin) works without noticing the difference. Who: Jan Kiszka <jan.kiszka@web.de> + +---------------------------- + +What: KVM memory aliases support +When: July 2010 +Why: Memory aliasing support is used for speeding up guest vga access + through the vga windows. + + Modern userspace no longer uses this feature, so it's just bitrotted + code and can be removed with no impact. +Who: Avi Kivity <avi@redhat.com> + +---------------------------- + +What: KVM kernel-allocated memory slots +When: July 2010 +Why: Since 2.6.25, kvm supports user-allocated memory slots, which are + much more flexible than kernel-allocated slots. All current userspace + supports the newer interface and this code can be removed with no + impact. +Who: Avi Kivity <avi@redhat.com> + +---------------------------- + +What: KVM paravirt mmu host support +When: January 2011 +Why: The paravirt mmu host support is slower than non-paravirt mmu, both + on newer and older hardware. It is already not exposed to the guest, + and kept only for live migration purposes. +Who: Avi Kivity <avi@redhat.com> + +---------------------------- diff --git a/Documentation/filesystems/nilfs2.txt b/Documentation/filesystems/nilfs2.txt index 839efd8a8a8..cf6d0d85ca8 100644 --- a/Documentation/filesystems/nilfs2.txt +++ b/Documentation/filesystems/nilfs2.txt @@ -74,6 +74,9 @@ norecovery Disable recovery of the filesystem on mount. This disables every write access on the device for read-only mounts or snapshots. This option will fail for r/w mounts on an unclean volume. +discard Issue discard/TRIM commands to the underlying block + device when blocks are freed. This is useful for SSD + devices and sparse/thinly-provisioned LUNs. NILFS2 usage ============ diff --git a/Documentation/filesystems/sharedsubtree.txt b/Documentation/filesystems/sharedsubtree.txt index 23a181074f9..fc0e39af43c 100644 --- a/Documentation/filesystems/sharedsubtree.txt +++ b/Documentation/filesystems/sharedsubtree.txt @@ -837,6 +837,9 @@ replicas continue to be exactly same. individual lists does not affect propagation or the way propagation tree is modified by operations. + All vfsmounts in a peer group have the same ->mnt_master. If it is + non-NULL, they form a contiguous (ordered) segment of slave list. + A example propagation tree looks as shown in the figure below. [ NOTE: Though it looks like a forest, if we consider all the shared mounts as a conceptual entity called 'pnode', it becomes a tree] @@ -874,8 +877,19 @@ replicas continue to be exactly same. NOTE: The propagation tree is orthogonal to the mount tree. +8B Locking: + + ->mnt_share, ->mnt_slave, ->mnt_slave_list, ->mnt_master are protected + by namespace_sem (exclusive for modifications, shared for reading). + + Normally we have ->mnt_flags modifications serialized by vfsmount_lock. + There are two exceptions: do_add_mount() and clone_mnt(). + The former modifies a vfsmount that has not been visible in any shared + data structures yet. + The latter holds namespace_sem and the only references to vfsmount + are in lists that can't be traversed without namespace_sem. -8B Algorithm: +8C Algorithm: The crux of the implementation resides in rbind/move operation. diff --git a/Documentation/i2c/busses/i2c-i801 b/Documentation/i2c/busses/i2c-i801 index 81c0c59a60e..e1bb5b26169 100644 --- a/Documentation/i2c/busses/i2c-i801 +++ b/Documentation/i2c/busses/i2c-i801 @@ -15,7 +15,8 @@ Supported adapters: * Intel 82801I (ICH9) * Intel EP80579 (Tolapai) * Intel 82801JI (ICH10) - * Intel PCH + * Intel 3400/5 Series (PCH) + * Intel Cougar Point (PCH) Datasheets: Publicly available at the Intel website Authors: diff --git a/Documentation/i2c/busses/i2c-parport b/Documentation/i2c/busses/i2c-parport index dceaba1ad93..2461c7b53b2 100644 --- a/Documentation/i2c/busses/i2c-parport +++ b/Documentation/i2c/busses/i2c-parport @@ -29,6 +29,9 @@ can be easily added when needed. Earlier kernels defaulted to type=0 (Philips). But now, if the type parameter is missing, the driver will simply fail to initialize. +SMBus alert support is available on adapters which have this line properly +connected to the parallel port's interrupt pin. + Building your own adapter ------------------------- diff --git a/Documentation/i2c/busses/i2c-parport-light b/Documentation/i2c/busses/i2c-parport-light index 28743647852..bdc9cbb2e0f 100644 --- a/Documentation/i2c/busses/i2c-parport-light +++ b/Documentation/i2c/busses/i2c-parport-light @@ -9,3 +9,14 @@ parport handling is not an option. The drawback is a reduced portability and the impossibility to daisy-chain other parallel port devices. Please see i2c-parport for documentation. + +Module parameters: + +* type: type of adapter (see i2c-parport or modinfo) + +* base: base I/O address + Default is 0x378 which is fairly common for parallel ports, at least on PC. + +* irq: optional IRQ + This must be passed if you want SMBus alert support, assuming your adapter + actually supports this. diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol index 9df47441f0e..7c19d1a2bea 100644 --- a/Documentation/i2c/smbus-protocol +++ b/Documentation/i2c/smbus-protocol @@ -185,6 +185,22 @@ the protocol. All ARP communications use slave address 0x61 and require PEC checksums. +SMBus Alert +=========== + +SMBus Alert was introduced in Revision 1.0 of the specification. + +The SMBus alert protocol allows several SMBus slave devices to share a +single interrupt pin on the SMBus master, while still allowing the master +to know which slave triggered the interrupt. + +This is implemented the following way in the Linux kernel: +* I2C bus drivers which support SMBus alert should call + i2c_setup_smbus_alert() to setup SMBus alert support. +* I2C drivers for devices which can trigger SMBus alerts should implement + the optional alert() callback. + + I2C Block Transactions ====================== diff --git a/Documentation/i2c/writing-clients b/Documentation/i2c/writing-clients index 0a74603eb67..3219ee0dbfe 100644 --- a/Documentation/i2c/writing-clients +++ b/Documentation/i2c/writing-clients @@ -318,8 +318,9 @@ Plain I2C communication These routines read and write some bytes from/to a client. The client contains the i2c address, so you do not have to include it. The second parameter contains the bytes to read/write, the third the number of bytes -to read/write (must be less than the length of the buffer.) Returned is -the actual number of bytes read/written. +to read/write (must be less than the length of the buffer, also should be +less than 64k since msg.len is u16.) Returned is the actual number of bytes +read/written. int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num); diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt index 35cf64d4436..35c9b51d20e 100644 --- a/Documentation/ioctl/ioctl-number.txt +++ b/Documentation/ioctl/ioctl-number.txt @@ -139,7 +139,6 @@ Code Seq#(hex) Include File Comments 'K' all linux/kd.h 'L' 00-1F linux/loop.h conflict! 'L' 10-1F drivers/scsi/mpt2sas/mpt2sas_ctl.h conflict! -'L' 20-2F linux/usb/vstusb.h 'L' E0-FF linux/ppdd.h encrypted disk device driver <http://linux01.gwdg.de/~alatham/ppdd.html> 'M' all linux/soundcard.h conflict! diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index fbcddc5abe2..d80930d58da 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1794,6 +1794,12 @@ and is between 256 and 4096 characters. It is defined in the file purges which is reported from either PAL_VM_SUMMARY or SAL PALO. + nr_cpus= [SMP] Maximum number of processors that an SMP kernel + could support. nr_cpus=n : n >= 1 limits the kernel to + supporting 'n' processors. Later in runtime you can not + use hotplug cpu feature to put more cpu back to online. + just like you compile the kernel NR_CPUS=n + nr_uarts= [SERIAL] maximum number of UARTs to be registered. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt index 053037a1fe6..2f9115c0ae6 100644 --- a/Documentation/kprobes.txt +++ b/Documentation/kprobes.txt @@ -1,6 +1,7 @@ Title : Kernel Probes (Kprobes) Authors : Jim Keniston <jkenisto@us.ibm.com> - : Prasanna S Panchamukhi <prasanna@in.ibm.com> + : Prasanna S Panchamukhi <prasanna.panchamukhi@gmail.com> + : Masami Hiramatsu <mhiramat@redhat.com> CONTENTS @@ -15,6 +16,7 @@ CONTENTS 9. Jprobes Example 10. Kretprobes Example Appendix A: The kprobes debugfs interface +Appendix B: The kprobes sysctl interface 1. Concepts: Kprobes, Jprobes, Return Probes @@ -42,13 +44,13 @@ registration/unregistration of a group of *probes. These functions can speed up unregistration process when you have to unregister a lot of probes at once. -The next three subsections explain how the different types of -probes work. They explain certain things that you'll need to -know in order to make the best use of Kprobes -- e.g., the -difference between a pre_handler and a post_handler, and how -to use the maxactive and nmissed fields of a kretprobe. But -if you're in a hurry to start using Kprobes, you can skip ahead -to section 2. +The next four subsections explain how the different types of +probes work and how jump optimization works. They explain certain +things that you'll need to know in order to make the best use of +Kprobes -- e.g., the difference between a pre_handler and +a post_handler, and how to use the maxactive and nmissed fields of +a kretprobe. But if you're in a hurry to start using Kprobes, you +can skip ahead to section 2. 1.1 How Does a Kprobe Work? @@ -161,13 +163,125 @@ In case probed function is entered but there is no kretprobe_instance object available, then in addition to incrementing the nmissed count, the user entry_handler invocation is also skipped. +1.4 How Does Jump Optimization Work? + +If you configured your kernel with CONFIG_OPTPROBES=y (currently +this option is supported on x86/x86-64, non-preemptive kernel) and +the "debug.kprobes_optimization" kernel parameter is set to 1 (see +sysctl(8)), Kprobes tries to reduce probe-hit overhead by using a jump +instruction instead of a breakpoint instruction at each probepoint. + +1.4.1 Init a Kprobe + +When a probe is registered, before attempting this optimization, +Kprobes inserts an ordinary, breakpoint-based kprobe at the specified +address. So, even if it's not possible to optimize this particular +probepoint, there'll be a probe there. + +1.4.2 Safety Check + +Before optimizing a probe, Kprobes performs the following safety checks: + +- Kprobes verifies that the region that will be replaced by the jump +instruction (the "optimized region") lies entirely within one function. +(A jump instruction is multiple bytes, and so may overlay multiple +instructions.) + +- Kprobes analyzes the entire function and verifies that there is no +jump into the optimized region. Specifically: + - the function contains no indirect jump; + - the function contains no instruction that causes an exception (since + the fixup code triggered by the exception could jump back into the + optimized region -- Kprobes checks the exception tables to verify this); + and + - there is no near jump to the optimized region (other than to the first + byte). + +- For each instruction in the optimized region, Kprobes verifies that +the instruction can be executed out of line. + +1.4.3 Preparing Detour Buffer + +Next, Kprobes prepares a "detour" buffer, which contains the following +instruction sequence: +- code to push the CPU's registers (emulating a breakpoint trap) +- a call to the trampoline code which calls user's probe handlers. +- code to restore registers +- the instructions from the optimized region +- a jump back to the original execution path. + +1.4.4 Pre-optimization + +After preparing the detour buffer, Kprobes verifies that none of the +following situations exist: +- The probe has either a break_handler (i.e., it's a jprobe) or a +post_handler. +- Other instructions in the optimized region are probed. +- The probe is disabled. +In any of the above cases, Kprobes won't start optimizing the probe. +Since these are temporary situations, Kprobes tries to start +optimizing it again if the situation is changed. + +If the kprobe can be optimized, Kprobes enqueues the kprobe to an +optimizing list, and kicks the kprobe-optimizer workqueue to optimize +it. If the to-be-optimized probepoint is hit before being optimized, +Kprobes returns control to the original instruction path by setting +the CPU's instruction pointer to the copied code in the detour buffer +-- thus at least avoiding the single-step. + +1.4.5 Optimization + +The Kprobe-optimizer doesn't insert the jump instruction immediately; +rather, it calls synchronize_sched() for safety first, because it's +possible for a CPU to be interrupted in the middle of executing the +optimized region(*). As you know, synchronize_sched() can ensure +that all interruptions that were active when synchronize_sched() +was called are done, but only if CONFIG_PREEMPT=n. So, this version +of kprobe optimization supports only kernels with CONFIG_PREEMPT=n.(**) + +After that, the Kprobe-optimizer calls stop_machine() to replace +the optimized region with a jump instruction to the detour buffer, +using text_poke_smp(). + +1.4.6 Unoptimization + +When an optimized kprobe is unregistered, disabled, or blocked by +another kprobe, it will be unoptimized. If this happens before +the optimization is complete, the kprobe is just dequeued from the +optimized list. If the optimization has been done, the jump is +replaced with the original code (except for an int3 breakpoint in +the first byte) by using text_poke_smp(). + +(*)Please imagine that the 2nd instruction is interrupted and then +the optimizer replaces the 2nd instruction with the jump *address* +while the interrupt handler is running. When the interrupt +returns to original address, there is no valid instruction, +and it causes an unexpected result. + +(**)This optimization-safety checking may be replaced with the +stop-machine method that ksplice uses for supporting a CONFIG_PREEMPT=y +kernel. + +NOTE for geeks: +The jump optimization changes the kprobe's pre_handler behavior. +Without optimization, the pre_handler can change the kernel's execution +path by changing regs->ip and returning 1. However, when the probe +is optimized, that modification is ignored. Thus, if you want to +tweak the kernel's execution path, you need to suppress optimization, +using one of the following techniques: +- Specify an empty function for the kprobe's post_handler or break_handler. + or +- Config CONFIG_OPTPROBES=n. + or +- Execute 'sysctl -w debug.kprobes_optimization=n' + 2. Architectures Supported Kprobes, jprobes, and return probes are implemented on the following architectures: -- i386 -- x86_64 (AMD-64, EM64T) +- i386 (Supports jump optimization) +- x86_64 (AMD-64, EM64T) (Supports jump optimization) - ppc64 - ia64 (Does not support probes on instruction slot1.) - sparc64 (Return probes not yet implemented.) @@ -193,6 +307,10 @@ it useful to "Compile the kernel with debug info" (CONFIG_DEBUG_INFO), so you can use "objdump -d -l vmlinux" to see the source-to-object code mapping. +If you want to reduce probing overhead, set "Kprobes jump optimization +support" (CONFIG_OPTPROBES) to "y". You can find this option under the +"Kprobes" line. + 4. API Reference The Kprobes API includes a "register" function and an "unregister" @@ -389,7 +507,10 @@ the probe which has been registered. Kprobes allows multiple probes at the same address. Currently, however, there cannot be multiple jprobes on the same function at -the same time. +the same time. Also, a probepoint for which there is a jprobe or +a post_handler cannot be optimized. So if you install a jprobe, +or a kprobe with a post_handler, at an optimized probepoint, the +probepoint will be unoptimized automatically. In general, you can install a probe anywhere in the kernel. In particular, you can probe interrupt handlers. Known exceptions @@ -453,6 +574,38 @@ reason, Kprobes doesn't support return probes (or kprobes or jprobes) on the x86_64 version of __switch_to(); the registration functions return -EINVAL. +On x86/x86-64, since the Jump Optimization of Kprobes modifies +instructions widely, there are some limitations to optimization. To +explain it, we introduce some terminology. Imagine a 3-instruction +sequence consisting of a two 2-byte instructions and one 3-byte +instruction. + + IA + | +[-2][-1][0][1][2][3][4][5][6][7] + [ins1][ins2][ ins3 ] + [<- DCR ->] + [<- JTPR ->] + +ins1: 1st Instruction +ins2: 2nd Instruction +ins3: 3rd Instruction +IA: Insertion Address +JTPR: Jump Target Prohibition Region +DCR: Detoured Code Region + +The instructions in DCR are copied to the out-of-line buffer +of the kprobe, because the bytes in DCR are replaced by +a 5-byte jump instruction. So there are several limitations. + +a) The instructions in DCR must be relocatable. +b) The instructions in DCR must not include a call instruction. +c) JTPR must not be targeted by any jump or call instruction. +d) DCR must not straddle the border betweeen functions. + +Anyway, these limitations are checked by the in-kernel instruction +decoder, so you don't need to worry about that. + 6. Probe Overhead On a typical CPU in use in 2005, a kprobe hit takes 0.5 to 1.0 @@ -476,6 +629,19 @@ k = 0.49 usec; j = 0.76; r = 0.80; kr = 0.82; jr = 1.07 ppc64: POWER5 (gr), 1656 MHz (SMT disabled, 1 virtual CPU per physical CPU) k = 0.77 usec; j = 1.31; r = 1.26; kr = 1.45; jr = 1.99 +6.1 Optimized Probe Overhead + +Typically, an optimized kprobe hit takes 0.07 to 0.1 microseconds to +process. Here are sample overhead figures (in usec) for x86 architectures. +k = unoptimized kprobe, b = boosted (single-step skipped), o = optimized kprobe, +r = unoptimized kretprobe, rb = boosted kretprobe, ro = optimized kretprobe. + +i386: Intel(R) Xeon(R) E5410, 2.33GHz, 4656.90 bogomips +k = 0.80 usec; b = 0.33; o = 0.05; r = 1.10; rb = 0.61; ro = 0.33 + +x86-64: Intel(R) Xeon(R) E5410, 2.33GHz, 4656.90 bogomips +k = 0.99 usec; b = 0.43; o = 0.06; r = 1.24; rb = 0.68; ro = 0.30 + 7. TODO a. SystemTap (http://sourceware.org/systemtap): Provides a simplified @@ -523,7 +689,8 @@ is also specified. Following columns show probe status. If the probe is on a virtual address that is no longer valid (module init sections, module virtual addresses that correspond to modules that've been unloaded), such probes are marked with [GONE]. If the probe is temporarily disabled, -such probes are marked with [DISABLED]. +such probes are marked with [DISABLED]. If the probe is optimized, it is +marked with [OPTIMIZED]. /sys/kernel/debug/kprobes/enabled: Turn kprobes ON/OFF forcibly. @@ -533,3 +700,19 @@ registered probes will be disarmed, till such time a "1" is echoed to this file. Note that this knob just disarms and arms all kprobes and doesn't change each probe's disabling state. This means that disabled kprobes (marked [DISABLED]) will be not enabled if you turn ON all kprobes by this knob. + + +Appendix B: The kprobes sysctl interface + +/proc/sys/debug/kprobes-optimization: Turn kprobes optimization ON/OFF. + +When CONFIG_OPTPROBES=y, this sysctl interface appears and it provides +a knob to globally and forcibly turn jump optimization (see section +1.4) ON or OFF. By default, jump optimization is allowed (ON). +If you echo "0" to this file or set "debug.kprobes_optimization" to +0 via sysctl, all optimized probes will be unoptimized, and any new +probes registered after that will not be optimized. Note that this +knob *changes* the optimized state. This means that optimized probes +(marked [OPTIMIZED]) will be unoptimized ([OPTIMIZED] tag will be +removed). If the knob is turned on, they will be optimized again. + diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt index 2811e452f75..c6416a39816 100644 --- a/Documentation/kvm/api.txt +++ b/Documentation/kvm/api.txt @@ -23,12 +23,12 @@ of a virtual machine. The ioctls belong to three classes Only run vcpu ioctls from the same thread that was used to create the vcpu. -2. File descritpors +2. File descriptors The kvm API is centered around file descriptors. An initial open("/dev/kvm") obtains a handle to the kvm subsystem; this handle can be used to issue system ioctls. A KVM_CREATE_VM ioctl on this -handle will create a VM file descripror which can be used to issue VM +handle will create a VM file descriptor which can be used to issue VM ioctls. A KVM_CREATE_VCPU ioctl on a VM fd will create a virtual cpu and return a file descriptor pointing to it. Finally, ioctls on a vcpu fd can be used to control the vcpu, including the important task of @@ -643,7 +643,7 @@ Type: vm ioctl Parameters: struct kvm_clock_data (in) Returns: 0 on success, -1 on error -Sets the current timestamp of kvmclock to the valued specific in its parameter. +Sets the current timestamp of kvmclock to the value specified in its parameter. In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios such as migration. @@ -795,11 +795,11 @@ Unused. __u64 data_offset; /* relative to kvm_run start */ } io; -If exit_reason is KVM_EXIT_IO_IN or KVM_EXIT_IO_OUT, then the vcpu has +If exit_reason is KVM_EXIT_IO, then the vcpu has executed a port I/O instruction which could not be satisfied by kvm. data_offset describes where the data is located (KVM_EXIT_IO_OUT) or where kvm expects application code to place the data for the next -KVM_RUN invocation (KVM_EXIT_IO_IN). Data format is a patcked array. +KVM_RUN invocation (KVM_EXIT_IO_IN). Data format is a packed array. struct { struct kvm_debug_exit_arch arch; @@ -815,7 +815,7 @@ Unused. __u8 is_write; } mmio; -If exit_reason is KVM_EXIT_MMIO or KVM_EXIT_IO_OUT, then the vcpu has +If exit_reason is KVM_EXIT_MMIO, then the vcpu has executed a memory-mapped I/O instruction which could not be satisfied by kvm. The 'data' member contains the written data if 'is_write' is true, and should be filled by application code otherwise. diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt index 75afa1229fd..39c0a09d010 100644 --- a/Documentation/laptops/thinkpad-acpi.txt +++ b/Documentation/laptops/thinkpad-acpi.txt @@ -650,6 +650,10 @@ LCD, CRT or DVI (if available). The following commands are available: echo expand_toggle > /proc/acpi/ibm/video echo video_switch > /proc/acpi/ibm/video +NOTE: Access to this feature is restricted to processes owning the +CAP_SYS_ADMIN capability for safety reasons, as it can interact badly +enough with some versions of X.org to crash it. + Each video output device can be enabled or disabled individually. Reading /proc/acpi/ibm/video shows the status of each device. diff --git a/Documentation/networking/00-INDEX b/Documentation/networking/00-INDEX index 50189bf07d5..fe5c099b8fc 100644 --- a/Documentation/networking/00-INDEX +++ b/Documentation/networking/00-INDEX @@ -32,6 +32,8 @@ cs89x0.txt - the Crystal LAN (CS8900/20-based) Ethernet ISA adapter driver cxacru.txt - Conexant AccessRunner USB ADSL Modem +cxacru-cf.py + - Conexant AccessRunner USB ADSL Modem configuration file parser de4x5.txt - the Digital EtherWORKS DE4?? and DE5?? PCI Ethernet driver decnet.txt diff --git a/Documentation/networking/cxacru-cf.py b/Documentation/networking/cxacru-cf.py new file mode 100644 index 00000000000..b41d298398c --- /dev/null +++ b/Documentation/networking/cxacru-cf.py @@ -0,0 +1,48 @@ +#!/usr/bin/env python +# Copyright 2009 Simon Arlott +# +# This program is free software; you can redistribute it and/or modify it +# under the terms of the GNU General Public License as published by the Free +# Software Foundation; either version 2 of the License, or (at your option) +# any later version. +# +# This program is distributed in the hope that it will be useful, but WITHOUT +# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or +# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for +# more details. +# +# You should have received a copy of the GNU General Public License along with +# this program; if not, write to the Free Software Foundation, Inc., 59 +# Temple Place - Suite 330, Boston, MA 02111-1307, USA. +# +# Usage: cxacru-cf.py < cxacru-cf.bin +# Output: values string suitable for the sysfs adsl_config attribute +# +# Warning: cxacru-cf.bin with MD5 hash cdbac2689969d5ed5d4850f117702110 +# contains mis-aligned values which will stop the modem from being able +# to make a connection. If the first and last two bytes are removed then +# the values become valid, but the modulation will be forced to ANSI +# T1.413 only which may not be appropriate. +# +# The original binary format is a packed list of le32 values. + +import sys +import struct + +i = 0 +while True: + buf = sys.stdin.read(4) + + if len(buf) == 0: + break + elif len(buf) != 4: + sys.stdout.write("\n") + sys.stderr.write("Error: read {0} not 4 bytes\n".format(len(buf))) + sys.exit(1) + + if i > 0: + sys.stdout.write(" ") + sys.stdout.write("{0:x}={1}".format(i, struct.unpack("<I", buf)[0])) + i += 1 + +sys.stdout.write("\n") diff --git a/Documentation/networking/cxacru.txt b/Documentation/networking/cxacru.txt index b074681a963..2cce04457b4 100644 --- a/Documentation/networking/cxacru.txt +++ b/Documentation/networking/cxacru.txt @@ -4,6 +4,12 @@ While it is capable of managing/maintaining the ADSL connection without the module loaded, the device will sometimes stop responding after unloading the driver and it is necessary to unplug/remove power to the device to fix this. +Note: support for cxacru-cf.bin has been removed. It was not loaded correctly +so it had no effect on the device configuration. Fixing it could have stopped +existing devices working when an invalid configuration is supplied. + +There is a script cxacru-cf.py to convert an existing file to the sysfs form. + Detected devices will appear as ATM devices named "cxacru". In /sys/class/atm/ these are directories named cxacruN where N is the device number. A symlink named device points to the USB interface device's directory which contains @@ -15,6 +21,15 @@ several sysfs attribute files for retrieving device statistics: * adsl_headend_environment Information about the remote headend. +* adsl_config + Configuration writing interface. + Write parameters in hexadecimal format <index>=<value>, + separated by whitespace, e.g.: + "1=0 a=5" + Up to 7 parameters at a time will be sent and the modem will restart + the ADSL connection when any value is set. These are logged for future + reference. + * downstream_attenuation (dB) * downstream_bits_per_frame * downstream_rate (kbps) @@ -61,6 +76,7 @@ several sysfs attribute files for retrieving device statistics: * mac_address * modulation + "" (when not connected) "ANSI T1.413" "ITU-T G.992.1 (G.DMT)" "ITU-T G.992.2 (G.LITE)" diff --git a/Documentation/powerpc/dts-bindings/fsl/dma.txt b/Documentation/powerpc/dts-bindings/fsl/dma.txt index 0732cdd05ba..2a4b4bce611 100644 --- a/Documentation/powerpc/dts-bindings/fsl/dma.txt +++ b/Documentation/powerpc/dts-bindings/fsl/dma.txt @@ -44,21 +44,29 @@ Example: compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel"; cell-index = <0>; reg = <0 0x80>; + interrupt-parent = <&ipic>; + interrupts = <71 8>; }; dma-channel@80 { compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel"; cell-index = <1>; reg = <0x80 0x80>; + interrupt-parent = <&ipic>; + interrupts = <71 8>; }; dma-channel@100 { compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel"; cell-index = <2>; reg = <0x100 0x80>; + interrupt-parent = <&ipic>; + interrupts = <71 8>; }; dma-channel@180 { compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel"; cell-index = <3>; reg = <0x180 0x80>; + interrupt-parent = <&ipic>; + interrupts = <71 8>; }; }; diff --git a/Documentation/usb/error-codes.txt b/Documentation/usb/error-codes.txt index 9cf83e8c27b..d83703ea74b 100644 --- a/Documentation/usb/error-codes.txt +++ b/Documentation/usb/error-codes.txt @@ -41,8 +41,8 @@ USB-specific: -EFBIG Host controller driver can't schedule that many ISO frames. --EPIPE Specified endpoint is stalled. For non-control endpoints, - reset this status with usb_clear_halt(). +-EPIPE The pipe type specified in the URB doesn't match the + endpoint's actual type. -EMSGSIZE (a) endpoint maxpacket size is zero; it is not usable in the current interface altsetting. @@ -60,6 +60,8 @@ USB-specific: -EHOSTUNREACH URB was rejected because the device is suspended. +-ENOEXEC A control URB doesn't contain a Setup packet. + ************************************************************************** * Error codes returned by in urb->status * diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt index 3bf6818c8cf..2790ad48cfc 100644 --- a/Documentation/usb/power-management.txt +++ b/Documentation/usb/power-management.txt @@ -2,7 +2,7 @@ Alan Stern <stern@rowland.harvard.edu> - November 10, 2009 + December 11, 2009 @@ -29,9 +29,9 @@ covered to some extent (see Documentation/power/*.txt for more information about system PM). Note: Dynamic PM support for USB is present only if the kernel was -built with CONFIG_USB_SUSPEND enabled. System PM support is present -only if the kernel was built with CONFIG_SUSPEND or CONFIG_HIBERNATION -enabled. +built with CONFIG_USB_SUSPEND enabled (which depends on +CONFIG_PM_RUNTIME). System PM support is present only if the kernel +was built with CONFIG_SUSPEND or CONFIG_HIBERNATION enabled. What is Remote Wakeup? @@ -229,6 +229,11 @@ necessary operations by hand or add them to a udev script. You can also change the idle-delay time; 2 seconds is not the best choice for every device. +If a driver knows that its device has proper suspend/resume support, +it can enable autosuspend all by itself. For example, the video +driver for a laptop's webcam might do this, since these devices are +rarely used and so should normally be autosuspended. + Sometimes it turns out that even when a device does work okay with autosuspend there are still problems. For example, there are experimental patches adding autosuspend support to the usbhid driver, @@ -321,69 +326,81 @@ driver does so by calling these six functions: void usb_autopm_get_interface_no_resume(struct usb_interface *intf); void usb_autopm_put_interface_no_suspend(struct usb_interface *intf); -The functions work by maintaining a counter in the usb_interface -structure. When intf->pm_usage_count is > 0 then the interface is -deemed to be busy, and the kernel will not autosuspend the interface's -device. When intf->pm_usage_count is <= 0 then the interface is -considered to be idle, and the kernel may autosuspend the device. +The functions work by maintaining a usage counter in the +usb_interface's embedded device structure. When the counter is > 0 +then the interface is deemed to be busy, and the kernel will not +autosuspend the interface's device. When the usage counter is = 0 +then the interface is considered to be idle, and the kernel may +autosuspend the device. -(There is a similar pm_usage_count field in struct usb_device, +(There is a similar usage counter field in struct usb_device, associated with the device itself rather than any of its interfaces. -This field is used only by the USB core.) - -Drivers must not modify intf->pm_usage_count directly; its value -should be changed only be using the functions listed above. Drivers -are responsible for insuring that the overall change to pm_usage_count -during their lifetime balances out to 0 (it may be necessary for the -disconnect method to call usb_autopm_put_interface() one or more times -to fulfill this requirement). The first two routines use the PM mutex -in struct usb_device for mutual exclusion; drivers using the async -routines are responsible for their own synchronization and mutual -exclusion. - - usb_autopm_get_interface() increments pm_usage_count and - attempts an autoresume if the new value is > 0 and the - device is suspended. - - usb_autopm_put_interface() decrements pm_usage_count and - attempts an autosuspend if the new value is <= 0 and the - device isn't suspended. +This counter is used only by the USB core.) + +Drivers need not be concerned about balancing changes to the usage +counter; the USB core will undo any remaining "get"s when a driver +is unbound from its interface. As a corollary, drivers must not call +any of the usb_autopm_* functions after their diconnect() routine has +returned. + +Drivers using the async routines are responsible for their own +synchronization and mutual exclusion. + + usb_autopm_get_interface() increments the usage counter and + does an autoresume if the device is suspended. If the + autoresume fails, the counter is decremented back. + + usb_autopm_put_interface() decrements the usage counter and + attempts an autosuspend if the new value is = 0. usb_autopm_get_interface_async() and usb_autopm_put_interface_async() do almost the same things as - their non-async counterparts. The differences are: they do - not acquire the PM mutex, and they use a workqueue to do their + their non-async counterparts. The big difference is that they + use a workqueue to do the resume or suspend part of their jobs. As a result they can be called in an atomic context, such as an URB's completion handler, but when they return the - device will not generally not yet be in the desired state. + device will generally not yet be in the desired state. usb_autopm_get_interface_no_resume() and usb_autopm_put_interface_no_suspend() merely increment or - decrement the pm_usage_count value; they do not attempt to - carry out an autoresume or an autosuspend. Hence they can be - called in an atomic context. + decrement the usage counter; they do not attempt to carry out + an autoresume or an autosuspend. Hence they can be called in + an atomic context. -The conventional usage pattern is that a driver calls +The simplest usage pattern is that a driver calls usb_autopm_get_interface() in its open routine and -usb_autopm_put_interface() in its close or release routine. But -other patterns are possible. +usb_autopm_put_interface() in its close or release routine. But other +patterns are possible. The autosuspend attempts mentioned above will often fail for one reason or another. For example, the power/level attribute might be set to "on", or another interface in the same device might not be idle. This is perfectly normal. If the reason for failure was that -the device hasn't been idle for long enough, a delayed workqueue -routine is automatically set up to carry out the operation when the -autosuspend idle-delay has expired. +the device hasn't been idle for long enough, a timer is scheduled to +carry out the operation automatically when the autosuspend idle-delay +has expired. Autoresume attempts also can fail, although failure would mean that the device is no longer present or operating properly. Unlike -autosuspend, there's no delay for an autoresume. +autosuspend, there's no idle-delay for an autoresume. Other parts of the driver interface ----------------------------------- +Drivers can enable autosuspend for their devices by calling + + usb_enable_autosuspend(struct usb_device *udev); + +in their probe() routine, if they know that the device is capable of +suspending and resuming correctly. This is exactly equivalent to +writing "auto" to the device's power/level attribute. Likewise, +drivers can disable autosuspend by calling + + usb_disable_autosuspend(struct usb_device *udev); + +This is exactly the same as writing "on" to the power/level attribute. + Sometimes a driver needs to make sure that remote wakeup is enabled during autosuspend. For example, there's not much point autosuspending a keyboard if the user can't cause the keyboard to do a @@ -395,26 +412,27 @@ though, setting this flag won't cause the kernel to autoresume it. Normally a driver would set this flag in its probe method, at which time the device is guaranteed not to be autosuspended.) -The synchronous usb_autopm_* routines have to run in a sleepable -process context; they must not be called from an interrupt handler or -while holding a spinlock. In fact, the entire autosuspend mechanism -is not well geared toward interrupt-driven operation. However there -is one thing a driver can do in an interrupt handler: +If a driver does its I/O asynchronously in interrupt context, it +should call usb_autopm_get_interface_async() before starting output and +usb_autopm_put_interface_async() when the output queue drains. When +it receives an input event, it should call usb_mark_last_busy(struct usb_device *udev); -This sets udev->last_busy to the current time. udev->last_busy is the -field used for idle-delay calculations; updating it will cause any -pending autosuspend to be moved back. The usb_autopm_* routines will -also set the last_busy field to the current time. - -Calling urb_mark_last_busy() from within an URB completion handler is -subject to races: The kernel may have just finished deciding the -device has been idle for long enough but not yet gotten around to -calling the driver's suspend method. The driver would have to be -responsible for synchronizing its suspend method with its URB -completion handler and causing the autosuspend to fail with -EBUSY if -an URB had completed too recently. +in the event handler. This sets udev->last_busy to the current time. +udev->last_busy is the field used for idle-delay calculations; +updating it will cause any pending autosuspend to be moved back. Most +of the usb_autopm_* routines will also set the last_busy field to the +current time. + +Asynchronous operation is always subject to races. For example, a +driver may call one of the usb_autopm_*_interface_async() routines at +a time when the core has just finished deciding the device has been +idle for long enough but not yet gotten around to calling the driver's +suspend method. The suspend method must be responsible for +synchronizing with the output request routine and the URB completion +handler; it should cause autosuspends to fail with -EBUSY if the +driver needs to use the device. External suspend calls should never be allowed to fail in this way, only autosuspend calls. The driver can tell them apart by checking @@ -422,75 +440,23 @@ the PM_EVENT_AUTO bit in the message.event argument to the suspend method; this bit will be set for internal PM events (autosuspend) and clear for external PM events. -Many of the ingredients in the autosuspend framework are oriented -towards interfaces: The usb_interface structure contains the -pm_usage_cnt field, and the usb_autopm_* routines take an interface -pointer as their argument. But somewhat confusingly, a few of the -pieces (i.e., usb_mark_last_busy()) use the usb_device structure -instead. Drivers need to keep this straight; they can call -interface_to_usbdev() to find the device structure for a given -interface. - - Locking requirements - -------------------- + Mutual exclusion + ---------------- -All three suspend/resume methods are always called while holding the -usb_device's PM mutex. For external events -- but not necessarily for -autosuspend or autoresume -- the device semaphore (udev->dev.sem) will -also be held. This implies that external suspend/resume events are -mutually exclusive with calls to probe, disconnect, pre_reset, and -post_reset; the USB core guarantees that this is true of internal -suspend/resume events as well. +For external events -- but not necessarily for autosuspend or +autoresume -- the device semaphore (udev->dev.sem) will be held when a +suspend or resume method is called. This implies that external +suspend/resume events are mutually exclusive with calls to probe, +disconnect, pre_reset, and post_reset; the USB core guarantees that +this is true of autosuspend/autoresume events as well. If a driver wants to block all suspend/resume calls during some -critical section, it can simply acquire udev->pm_mutex. Note that -calls to resume may be triggered indirectly. Block IO due to memory -allocations can make the vm subsystem resume a device. Thus while -holding this lock you must not allocate memory with GFP_KERNEL or -GFP_NOFS. - -Alternatively, if the critical section might call some of the -usb_autopm_* routines, the driver can avoid deadlock by doing: - - down(&udev->dev.sem); - rc = usb_autopm_get_interface(intf); - -and at the end of the critical section: - - if (!rc) - usb_autopm_put_interface(intf); - up(&udev->dev.sem); - -Holding the device semaphore will block all external PM calls, and the -usb_autopm_get_interface() will prevent any internal PM calls, even if -it fails. (Exercise: Why?) - -The rules for locking order are: - - Never acquire any device semaphore while holding any PM mutex. - - Never acquire udev->pm_mutex while holding the PM mutex for - a device that isn't a descendant of udev. - -In other words, PM mutexes should only be acquired going up the device -tree, and they should be acquired only after locking all the device -semaphores you need to hold. These rules don't matter to drivers very -much; they usually affect just the USB core. - -Still, drivers do need to be careful. For example, many drivers use a -private mutex to synchronize their normal I/O activities with their -disconnect method. Now if the driver supports autosuspend then it -must call usb_autopm_put_interface() from somewhere -- maybe from its -close method. It should make the call while holding the private mutex, -since a driver shouldn't call any of the usb_autopm_* functions for an -interface from which it has been unbound. - -But the usb_autpm_* routines always acquire the device's PM mutex, and -consequently the locking order has to be: private mutex first, PM -mutex second. Since the suspend method is always called with the PM -mutex held, it mustn't try to acquire the private mutex. It has to -synchronize with the driver's I/O activities in some other way. +critical section, the best way is to lock the device and call +usb_autopm_get_interface() (and do the reverse at the end of the +critical section). Holding the device semaphore will block all +external PM calls, and the usb_autopm_get_interface() will prevent any +internal PM calls, even if it fails. (Exercise: Why?) Interaction between dynamic PM and system PM @@ -499,22 +465,11 @@ synchronize with the driver's I/O activities in some other way. Dynamic power management and system power management can interact in a couple of ways. -Firstly, a device may already be manually suspended or autosuspended -when a system suspend occurs. Since system suspends are supposed to -be as transparent as possible, the device should remain suspended -following the system resume. The 2.6.23 kernel obeys this principle -for manually suspended devices but not for autosuspended devices; they -do get resumed when the system wakes up. (Presumably they will be -autosuspended again after their idle-delay time expires.) In later -kernels this behavior will be fixed. - -(There is an exception. If a device would undergo a reset-resume -instead of a normal resume, and the device is enabled for remote -wakeup, then the reset-resume takes place even if the device was -already suspended when the system suspend began. The justification is -that a reset-resume is a kind of remote-wakeup event. Or to put it -another way, a device which needs a reset won't be able to generate -normal remote-wakeup signals, so it ought to be resumed immediately.) +Firstly, a device may already be autosuspended when a system suspend +occurs. Since system suspends are supposed to be as transparent as +possible, the device should remain suspended following the system +resume. But this theory may not work out well in practice; over time +the kernel's behavior in this regard has changed. Secondly, a dynamic power-management event may occur as a system suspend is underway. The window for this is short, since system |