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path: root/drivers/cpufreq/cpufreq_userspace.c
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2008-02-06[CPUFREQ] Eliminate cpufreq_userspace scaling_setspeed deadlockVenki Pallipadi
Eliminate cpufreq_userspace scaling_setspeed deadlock. Luming Yu recently uncovered yet another cpufreq related deadlock. One thread that continuously switches the governors and the other thread that repeatedly cats the contents of cpufreq directory causes both these threads to go into a deadlock. Detailed examination of the deadlock showed the exact flow before the deadlock as: Thread 1 Thread 2 ________ ________ cats files under /sys/devices/.../cpufreq/ Set governor to userspace Adds a new sysfs entry for scaling_setspeed cats files under /sys/devices/.../cpufreq/ Set governor to performance Holds cpufreq_rw_sem in write mode Sends a STOP notify to userspace governor cat /sys/devices/.../cpufreq/scaling_setspeed Gets a handle on the above sysfs entry with sysfs_get_active Blocks while trying to get cpufreq_rw_sem in read mode Remove a sysfs entry for scaling_setspeed Blocks on sysfs_deactivate while waiting for earlier get_active (on other thread) to drain At this point both threads go into deadlock and any other thread that tries to do anything with sysfs cpufreq will also block. There seems to be no easy way to avoid this deadlock as long as cpufreq_userspace adds/removes the sysfs entry under same kobject as cpufreq. Below patch moves scaling_setspeed to cpufreq.c, keeping it always and calling back the governor on read/write. This is the cleanest fix I could think of, even though adding two callbacks in governor structure just for this seems unnecessary. Note that the change makes scaling_setspeed under /sys/.../cpufreq permanent and returns <unsupported> when governor is not userspace. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Dave Jones <davej@redhat.com>
2008-01-17cpufreq: Initialise default governor before useJohannes Weiner
When the cpufreq driver starts up at boot time, it calls into the default governor which might not be initialised yet. This hurts when the governor's worker function relies on memory that is not yet set up by its init function. This migrates all governors from module_init() to fs_initcall() when being the default, as was already done in cpufreq_performance when it was the only possible choice. The performance governor is always initialized early because it might be used as fallback even when not being the default. Fixes at least one actual oops where ondemand is the default governor and cpufreq_governor_dbs() uses the uninitialised kondemand_wq work-queue during boot-time. Signed-off-by: Johannes Weiner <hannes@saeurebad.de> Cc: Dave Jones <davej@codemonkey.org.uk> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-12Merge master.kernel.org:/pub/scm/linux/kernel/git/davej/cpufreqLinus Torvalds
* master.kernel.org:/pub/scm/linux/kernel/git/davej/cpufreq: [CPUFREQ] Fix sysfs_create_file return value handling [CPUFREQ] ondemand: fix tickless accounting and software coordination bug [CPUFREQ] ondemand: add a check to avoid negative load calculation [CPUFREQ] Keep userspace governor quiet when it is not being used [CPUFREQ] Longhaul - Proper register access [CPUFREQ] Kconfig powernow-k8 driver should depend on ACPI P-States driver [CPUFREQ] Longhaul - Replace ACPI functions with direct I/O [CPUFREQ] Longhaul - Remove duplicate multipliers [CPUFREQ] Longhaul - Embedded "conservative" [CPUFREQ] acpi-cpufreq: Proper ReadModifyWrite of PERF_CTL MSR [CPUFREQ] check return value of sysfs_create_file [CPUFREQ] Longhaul - Check ACPI "BM DMA in progress" bit [CPUFREQ] Longhaul - Move old_ratio to correct place [CPUFREQ] Longhaul - VT8237 support [CPUFREQ] Longhaul - Use all kinds of support [CPUFREQ] powernow-k8: clarify number of cores.
2007-07-11sysfs: kill unnecessary attribute->ownerTejun Heo
sysfs is now completely out of driver/module lifetime game. After deletion, a sysfs node doesn't access anything outside sysfs proper, so there's no reason to hold onto the attribute owners. Note that often the wrong modules were accounted for as owners leading to accessing removed modules. This patch kills now unnecessary attribute->owner. Note that with this change, userland holding a sysfs node does not prevent the backing module from being unloaded. For more info regarding lifetime rule cleanup, please read the following message. http://article.gmane.org/gmane.linux.kernel/510293 (tweaked by Greg to not delete the field just yet, to make it easier to merge things properly.) Signed-off-by: Tejun Heo <htejun@gmail.com> Cc: Cornelia Huck <cornelia.huck@de.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2007-06-21[CPUFREQ] Keep userspace governor quiet when it is not being usedVenki Pallipadi
Userspace governor registers a frequency change notifier at init time, even when no CPU is set to userspace governor. Make it register only when atleast one CPU is using userspace. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Dave Jones <davej@redhat.com>
2007-02-10[CPUFREQ] Remove hotplug cpu crapDave Jones
The hotplug CPU locking in cpufreq is horrendous. No-one seems to care enough to fix it, so just remove it so that the 99.9% of the real world users of this code can use cpufreq without being bothered by warnings. Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Dave Jones <davej@redhat.com>
2006-10-21[CPUFREQ] handle sysfs errorsJeff Garzik
Signed-off-by: Jeff Garzik <jeff@garzik.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Dave Jones <davej@redhat.com>
2006-07-26[PATCH] Reorganize the cpufreq cpu hotplug locking to not be totally bizareArjan van de Ven
The patch below moves the cpu hotplugging higher up in the cpufreq layering; this is needed to avoid recursive taking of the cpu hotplug lock and to otherwise detangle the mess. The new rules are: 1. you must do lock_cpu_hotplug() around the following functions: __cpufreq_driver_target __cpufreq_governor (for CPUFREQ_GOV_LIMITS operation only) __cpufreq_set_policy 2. governer methods (.governer) must NOT take the lock_cpu_hotplug() lock in any way; they are called with the lock taken already 3. if your governer spawns a thread that does things, like calling __cpufreq_driver_target, your thread must honor rule #1. 4. the policy lock and other cpufreq internal locks nest within the lock_cpu_hotplug() lock. I'm not entirely happy about how the __cpufreq_governor rule ended up (conditional locking rule depending on the argument) but basically all callers pass this as a constant so it's not too horrible. The patch also removes the cpufreq_governor() function since during the locking audit it turned out to be entirely unused (so no need to fix it) The patch works on my testbox, but it could use more testing (otoh... it can't be much worse than the current code) Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-30Remove obsolete #include <linux/config.h>Jörn Engel
Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de> Signed-off-by: Adrian Bunk <bunk@stusta.de>
2006-02-28[CPUFREQ] Lots of whitespace & CodingStyle cleanup.Dave Jones
Signed-off-by: Dave Jones <davej@redhat.com>
2006-01-27[CPUFREQ] Get rid of userspace policy struct, make userspace gov _PPC safe.Thomas Renninger
Userspace governor need not to hold it's own cpufreq_policy, better make use of the global core policy. Also fixes a bug in case of frequency changes via _PPC. Old min/max values have wrongly been passed to __cpufreq_driver_target() (kind of buffered) and when max freq was available again, only the old max(normally lowest freq) was still active. Signed-off-by: Thomas Renninger <trenn@suse.de> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Dave Jones <davej@redhat.com> cpufreq_userspace.c | 53 +++++++++++++++++++++++++++------------------------- 1 files changed, 28 insertions(+), 25 deletions(-)
2006-01-18[CPUFREQ] Convert drivers/cpufreq semaphores to mutexes.akpm@osdl.org
Semaphore to mutex conversion. The conversion was generated via scripts, and the result was validated automatically via a script as well. Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Dave Jones <davej@redhat.com>
2005-04-16Linux-2.6.12-rc2Linus Torvalds
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!