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2008-07-11ftrace: define function trace nopSteven Rostedt
When CONFIG_FTRACE is not enabled, the tracing_start_functon_trace and tracing_stop_function_trace should be nops. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-11ftrace: move sched_switch enable after markersSteven Rostedt
We have two markers now that are enabled on sched_switch. One that records the context switching and the other that records task wake ups. Currently we enable the tracing first and then set the markers. This causes some confusing traces: # tracer: sched_switch # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | trace-cmd-3973 [00] 115.834817: 3973:120:R + 3: 0:S trace-cmd-3973 [01] 115.834910: 3973:120:R + 6: 0:S trace-cmd-3973 [02] 115.834910: 3973:120:R + 9: 0:S trace-cmd-3973 [03] 115.834910: 3973:120:R + 12: 0:S trace-cmd-3973 [02] 115.834910: 3973:120:R + 9: 0:S <idle>-0 [02] 115.834910: 0:140:R ==> 3973:120:R Here we see that trace-cmd with PID 3973 wakes up task 9 but the next line shows the idle task doing a context switch to task 3973. Enabling the tracing to _after_ the markers are set creates a much saner output: # tracer: sched_switch # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | <idle>-0 [02] 7922.634225: 0:140:R ==> 4790:120:R trace-cmd-4789 [03] 7922.634225: 0:140:R + 4790:120:R Signed-off-by: Steven Rostedt <srostedt@redhat.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-03ftrace: prevent ftrace modifications while being kprobe'd, v2Abhishek Sagar
add two missing chunks for ftrace+kprobe. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-01fix "ftrace: store mcount address in rec->ip"Ingo Molnar
Alexander Beregalov reported this build failure: $ make CROSS_COMPILE=sparc64-unknown-linux-gnu- image modules && sudo make modules_install CHK include/linux/version.h CHK include/linux/utsrelease.h CALL scripts/checksyscalls.sh CHK include/linux/compile.h dnsdomainname: Unknown host CC arch/sparc64/kernel/sparc64_ksyms.o arch/sparc64/kernel/sparc64_ksyms.c:116: error: '_mcount' undeclared here (not in a function) cc1: warnings being treated as errors arch/sparc64/kernel/sparc64_ksyms.c:116: error: type defaults to 'int' in declaration of '_mcount' And bisected it back to: | commit 395a59d0f8e86bb39cd700c3d185d30c670bb958 | Author: Abhishek Sagar <sagar.abhishek@gmail.com> | Date: Sat Jun 21 23:47:27 2008 +0530 | | ftrace: store mcount address in rec->ip the mcount prototype is only available under CONFIG_FTRACE, extend it to CONFIG_MCOUNT as well. Reported-and-bisected-by: Alexander Beregalov <a.beregalov@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-01mmiotrace broken in linux-next (8-bit writes only)Pekka Paalanen
The moment mmiotrace is enabled, I hit a NULL deref in: IP: [<ffffffff80256e71>] __trace_special+0x17c/0x23a Call Trace: [<ffffffff802573cc>] ftrace_special+0x6f/0x9a [<ffffffff8023e3e4>] down+0x19/0x4a [<ffffffff80228adc>] acquire_console_sem+0x42/0x58 [<ffffffff8035d273>] con_flush_chars+0x28/0x43 [<ffffffff80354a70>] write_chan+0x22e/0x334 [<ffffffff802244e9>] ? default_wake_function+0x0/0xf [<ffffffff8035236d>] tty_write+0x195/0x228 [<ffffffff80354842>] ? write_chan+0x0/0x334 [<ffffffff8027c23a>] vfs_write+0xae/0x137 [<ffffffff8027c6e3>] sys_write+0x47/0x70 [<ffffffff8020b1db>] system_call_after_swapgs+0x7b/0x80 which means 'entry' in __trace_special() is NULL. [ mingo@elte.hu: that ftrace_special() was a leftover. ] Signed-off-by: Pekka Paalanen <pq@iki.fi> Cc: Steven Rostedt <srostedt@redhat.com> Cc: proski@gnu.org Cc: "Vegard Nossum" <vegard.nossum@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-25Merge branch 'linus' into tracing/ftraceIngo Molnar
2008-06-24Linux 2.6.26-rc8Linus Torvalds
2008-06-24Merge branch 'release' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6 * 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6: [IA64] Eliminate NULL test after alloc_bootmem in iosapic_alloc_rte() [IA64] Handle count==0 in sn2_ptc_proc_write() [IA64] Fix boot failure on ia64/sn2
2008-06-24Merge git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6-fixesLinus Torvalds
* git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6-fixes: [GFS2] fix gfs2 block allocation (cleaned up) [GFS2] BUG: unable to handle kernel paging request at ffff81002690e000
2008-06-24Merge branch 'kvm-updates-2.6.26' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/avi/kvm * 'kvm-updates-2.6.26' of git://git.kernel.org/pub/scm/linux/kernel/git/avi/kvm: KVM: Remove now unused structs from kvm_para.h x86: KVM guest: Use the paravirt clocksource structs and functions KVM: Make kvm host use the paravirt clocksource structs x86: Make xen use the paravirt clocksource structs and functions x86: Add structs and functions for paravirt clocksource KVM: VMX: Fix host msr corruption with preemption enabled KVM: ioapic: fix lost interrupt when changing a device's irq KVM: MMU: Fix oops on guest userspace access to guest pagetable KVM: MMU: large page update_pte issue with non-PAE 32-bit guests (resend) KVM: MMU: Fix rmap_write_protect() hugepage iteration bug KVM: close timer injection race window in __vcpu_run KVM: Fix race between timer migration and vcpu migration
2008-06-24Merge git://git.kernel.org/pub/scm/linux/kernel/git/wim/linux-2.6-watchdogLinus Torvalds
* git://git.kernel.org/pub/scm/linux/kernel/git/wim/linux-2.6-watchdog: Revert "[WATCHDOG] hpwdt: Add CFLAGS to get driver working"
2008-06-24Merge branch 'x86-fixes-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: xen: remove support for non-PAE 32-bit
2008-06-24Merge branch 'for_linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb * 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb: kgdb: sparse fix kgdb: documentation update - remove kgdboe
2008-06-24enable bus mastering on i915 at resume timeJie Luo
On 9xx chips, bus mastering needs to be enabled at resume time for much of the chip to function. With this patch, vblank interrupts will work as expected on resume, along with other chip functions. Fixes kernel bugzilla #10844. Signed-off-by: Jie Luo <clotho67@gmail.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-06-24KVM: Remove now unused structs from kvm_para.hGerd Hoffmann
The kvm_* structs are obsoleted by the pvclock_* ones. Now all users have been switched over and the old structs can be dropped. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24x86: KVM guest: Use the paravirt clocksource structs and functionsGerd Hoffmann
This patch updates the kvm host code to use the pvclock structs and functions, thereby making it compatible with Xen. The patch also fixes an initialization bug: on SMP systems the per-cpu has two different locations early at boot and after CPU bringup. kvmclock must take that in account when registering the physical address within the host. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24KVM: Make kvm host use the paravirt clocksource structsGerd Hoffmann
This patch updates the kvm host code to use the pvclock structs. It also makes the paravirt clock compatible with Xen. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24x86: Make xen use the paravirt clocksource structs and functionsGerd Hoffmann
This patch updates the xen guest to use the pvclock structs and helper functions. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24x86: Add structs and functions for paravirt clocksourceGerd Hoffmann
This patch adds structs for the paravirt clocksource ABI used by both xen and kvm (pvclock-abi.h). It also adds some helper functions to read system time and wall clock time from a paravirtual clocksource (pvclock.[ch]). They are based on the xen code. They are enabled using CONFIG_PARAVIRT_CLOCK. Subsequent patches of this series will put the code in use. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24[GFS2] fix gfs2 block allocation (cleaned up)Benjamin Marzinski
This patch fixes bz 450641. This patch changes the computation for zero_metapath_length(), which it renames to metapath_branch_start(). When you are extending the metadata tree, The indirect blocks that point to the new data block must either diverge from the existing tree either at the inode, or at the first indirect block. They can diverge at the first indirect block because the inode has room for 483 pointers while the indirect blocks have room for 509 pointers, so when the tree is grown, there is some free space in the first indirect block. What metapath_branch_start() now computes is the height where the first indirect block for the new data block is located. It can either be 1 (if the indirect block diverges from the inode) or 2 (if it diverges from the first indirect block). Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
2008-06-24[IA64] Eliminate NULL test after alloc_bootmem in iosapic_alloc_rte()Julia Lawall
As noted by Akinobu Mita alloc_bootmem and related functions never return NULL and always return a zeroed region of memory. Thus a NULL test or memset after calls to these functions is unnecessary. Signed-off-by: Julia Lawall <julia@diku.dk> Signed-off-by: Tony Luck <tony.luck@intel.com>
2008-06-24[IA64] Handle count==0 in sn2_ptc_proc_write()Cliff Wickman
The fix applied in e0c6d97c65e0784aade7e97b9411f245a6c543e7 "security hole in sn2_ptc_proc_write" didn't take into account the case where count==0 (which results in a buffer underrun when adding the trailing '\0'). Thanks to Andi Kleen for pointing this out. Signed-off-by: Cliff Wickman <cpw@sgi.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
2008-06-24[IA64] Fix boot failure on ia64/sn2Jes Sorensen
Call check_sal_cache_flush() after platform_setup() as check_sal_cache_flush() now relies on being able to call platform vector code. Problem was introduced by: 3463a93def55c309f3c0d0a8aaf216be3be42d64 "Update check_sal_cache_flush to use platform_send_ipi()" Signed-off-by: Jes Sorensen <jes@sgi.com> Tested-by: Alex Chiang: <achiang@hp.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
2008-06-24kgdb: sparse fixJason Wessel
- Fix warning reported by sparse kernel/kgdb.c:1502:6: warning: symbol 'kgdb_console_write' was not declared. Should it be static? Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2008-06-24kgdb: documentation update - remove kgdboeJason Wessel
kgdboe is not presently included kgdb, and there should be no references to it. Also fix the tcp port terminal connection example. Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2008-06-24xen: remove support for non-PAE 32-bitJeremy Fitzhardinge
Non-PAE operation has been deprecated in Xen for a while, and is rarely tested or used. xen-unstable has now officially dropped non-PAE support. Since Xen/pvops' non-PAE support has also been broken for a while, we may as well completely drop it altogether. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-24[GFS2] BUG: unable to handle kernel paging request at ffff81002690e000Bob Peterson
This patch fixes bugzilla bug bz448866: gfs2: BUG: unable to handle kernel paging request at ffff81002690e000. Signed-off-by: Bob Peterson <rpeterso@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
2008-06-24Revert "[WATCHDOG] hpwdt: Add CFLAGS to get driver working"Wim Van Sebroeck
After Linus fixed the inline assembly, the CFLAGS option is not needed anymore. Signed-off-by: Thomas Mingarelli <Thomas.Mingarelli@hp.com> Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2008-06-24KVM: VMX: Fix host msr corruption with preemption enabledAvi Kivity
Switching msrs can occur either synchronously as a result of calls to the msr management functions (usually in response to the guest touching virtualized msrs), or asynchronously when preempting a kvm thread that has guest state loaded. If we're unlucky enough to have the two at the same time, host msrs are corrupted and the machine goes kaput on the next syscall. Most easily triggered by Windows Server 2008, as it does a lot of msr switching during bootup. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24KVM: ioapic: fix lost interrupt when changing a device's irqAvi Kivity
The ioapic acknowledge path translates interrupt vectors to irqs. It currently uses a first match algorithm, stopping when it finds the first redirection table entry containing the vector. That fails however if the guest changes the irq to a different line, leaving the old redirection table entry in place (though masked). Result is interrupts not making it to the guest. Fix by always scanning the entire redirection table. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24KVM: MMU: Fix oops on guest userspace access to guest pagetableAvi Kivity
KVM has a heuristic to unshadow guest pagetables when userspace accesses them, on the assumption that most guests do not allow userspace to access pagetables directly. Unfortunately, in addition to unshadowing the pagetables, it also oopses. This never triggers on ordinary guests since sane OSes will clear the pagetables before assigning them to userspace, which will trigger the flood heuristic, unshadowing the pagetables before the first userspace access. One particular guest, though (Xenner) will run the kernel in userspace, triggering the oops. Since the heuristic is incorrect in this case, we can simply remove it. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24KVM: MMU: large page update_pte issue with non-PAE 32-bit guests (resend)Marcelo Tosatti
kvm_mmu_pte_write() does not handle 32-bit non-PAE large page backed guests properly. It will instantiate two 2MB sptes pointing to the same physical 2MB page when a guest large pte update is trapped. Instead of duplicating code to handle this, disallow directory level updates to happen through kvm_mmu_pte_write(), so the two 2MB sptes emulating one guest 4MB pte can be correctly created by the page fault handling path. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24KVM: MMU: Fix rmap_write_protect() hugepage iteration bugMarcelo Tosatti
rmap_next() does not work correctly after rmap_remove(), as it expects the rmap chains not to change during iteration. Fix (for now) by restarting iteration from the beginning. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24KVM: close timer injection race window in __vcpu_runMarcelo Tosatti
If a timer fires after kvm_inject_pending_timer_irqs() but before local_irq_disable() the code will enter guest mode and only inject such timer interrupt the next time an unrelated event causes an exit. It would be simpler if the timer->pending irq conversion could be done with IRQ's disabled, so that the above problem cannot happen. For now introduce a new vcpu requests bit to cancel guest entry. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-24KVM: Fix race between timer migration and vcpu migrationMarcelo Tosatti
A guest vcpu instance can be scheduled to a different physical CPU between the test for KVM_REQ_MIGRATE_TIMER and local_irq_disable(). If that happens, the timer will only be migrated to the current pCPU on the next exit, meaning that guest LAPIC timer event can be delayed until a host interrupt is triggered. Fix it by cancelling guest entry if any vcpu request is pending. This has the side effect of nicely consolidating vcpu->requests checks. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-06-23alpha: fix compile error in arch/alpha/mm/init.cThorsten Kranzkowski
Commit 9267b4b3880d00dc2dab90f1d817c856939114f7 ("alpha: fix module load failures on smp (bug #10926)") causes a regression for my ev4 uniprocessor build: CC arch/alpha/mm/init.o /export/data/repositories/linux-2.6/arch/alpha/mm/init.c:34: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘typeof’ make[2]: *** [arch/alpha/mm/init.o] Error 1 make[1]: *** [arch/alpha/mm] Error 2 make: *** [sub-make] Error 2 This fixes it for me (compile and boot tested): Signed-off-by: Thorsten Kranzkowski <dl8bcu@dl8bcu.de> Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-06-23Merge branch 'hotfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6Linus Torvalds
* 'hotfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6: NFS: nfs_updatepage(): don't mark page as dirty if an error occurred NFS: Fix filehandle size comparisons in the mount code NFS: Reduce the NFS mount code stack usage.
2008-06-23NFS: nfs_updatepage(): don't mark page as dirty if an error occurredTrond Myklebust
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2008-06-23NFS: Fix filehandle size comparisons in the mount codeTrond Myklebust
Fix a sign issue in xdr_decode_fhstatus3() Fix incorrect comparison in nfs_validate_mount_data() Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2008-06-23NFS: Reduce the NFS mount code stack usage.Trond Myklebust
This appears to fix the Oops reported in http://bugzilla.kernel.org/show_bug.cgi?id=10826 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
2008-06-23ftrace: avoid modifying kprobe'd recordsAbhishek Sagar
Avoid modifying the mcount call-site if there is a kprobe installed on it. These records are not marked as failed however. This allowed the filter rules on them to remain up-to-date. Whenever the kprobe on the corresponding record is removed, the record gets updated as normal. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-23ftrace: freeze kprobe'd recordsAbhishek Sagar
Let records identified as being kprobe'd be marked as "frozen". The trouble with records which have a kprobe installed on their mcount call-site is that they don't get updated. So if such a function which is currently being traced gets its tracing disabled due to a new filter rule (or because it was added to the notrace list) then it won't be updated and continue being traced. This patch allows scanning of all frozen records during tracing to check if they should be traced. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-23kprobes: enable clean usage of get_kprobeAbhishek Sagar
Allow clean use of get_kprobe() outside of core kprobe code. Ftrace makes use of get_kprobe to identify probes installed on mcount call-sites. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Cc: Masami Hiramatsu <mhiramat@redhat.com> Cc: jkenisto@us.ibm.com Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-23ftrace: store mcount address in rec->ipAbhishek Sagar
Record the address of the mcount call-site. Currently all archs except sparc64 record the address of the instruction following the mcount call-site. Some general cleanups are entailed. Storing mcount addresses in rec->ip enables looking them up in the kprobe hash table later on to check if they're kprobe'd. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: davem@davemloft.net Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-23Merge branch 'core-fixes-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: futexes: fix fault handling in futex_lock_pi
2008-06-23Merge branch 'sched-fixes-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: sched: refactor wait_for_completion_timeout() sched: fix wait_for_completion_timeout() spurious failure under heavy load sched: rt: dont stop the period timer when there are tasks wanting to run
2008-06-23Merge branch 'x86-fixes-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: xen: don't drop NX bit xen: mask unwanted pte bits in __supported_pte_mask xen: Use wmb instead of rmb in xen_evtchn_do_upcall(). x86: fix NULL pointer deref in __switch_to
2008-06-23Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband: IB/mthca: Clear ICM pages before handing to FW
2008-06-23Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6 * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6: ALSA: sb - Fix wrong assertions ALSA: aw2 - Fix Oops at initialization
2008-06-23mm: fix race in COW logicNick Piggin
There is a race in the COW logic. It contains a shortcut to avoid the COW and reuse the page if we have the sole reference on the page, however it is possible to have two racing do_wp_page()ers with one causing the other to mistakenly believe it is safe to take the shortcut when it is not. This could lead to data corruption. Process 1 and process2 each have a wp pte of the same anon page (ie. one forked the other). The page's mapcount is 2. Then they both attempt to write to it around the same time... proc1 proc2 thr1 proc2 thr2 CPU0 CPU1 CPU3 do_wp_page() do_wp_page() trylock_page() can_share_swap_page() load page mapcount (==2) reuse = 0 pte unlock copy page to new_page pte lock page_remove_rmap(page); trylock_page() can_share_swap_page() load page mapcount (==1) reuse = 1 ptep_set_access_flags (allow W) write private key into page read from page ptep_clear_flush() set_pte_at(pte of new_page) Fix this by moving the page_remove_rmap of the old page after the pte clear and flush. Potentially the entire branch could be moved down here, but in order to stay consistent, I won't (should probably move all the *_mm_counter stuff with one patch). Signed-off-by: Nick Piggin <npiggin@suse.de> Acked-by: Hugh Dickins <hugh@veritas.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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