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On Thu, Sep 11, 2008 at 10:27:10AM +0200, Ingo Molnar wrote: > and it's working fine on most boxes. One testbox found this new locking > scenario: > > PM: Adding info for No Bus:vcsa7 > EDAC DEBUG: MC0: i82860_check() > > ======================================================= > [ INFO: possible circular locking dependency detected ] > 2.6.27-rc6-tip #1 > ------------------------------------------------------- > X/4873 is trying to acquire lock: > (&bb->mutex){--..}, at: [<c020ba20>] mmap+0x40/0xa0 > > but task is already holding lock: > (&mm->mmap_sem){----}, at: [<c0125a1e>] sys_mmap2+0x8e/0xc0 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (&mm->mmap_sem){----}: > [<c017dc96>] validate_chain+0xa96/0xf50 > [<c017ef2b>] __lock_acquire+0x2cb/0x5b0 > [<c017f299>] lock_acquire+0x89/0xc0 > [<c01aa8fb>] might_fault+0x6b/0x90 > [<c040b618>] copy_to_user+0x38/0x60 > [<c020bcfb>] read+0xfb/0x170 > [<c01c09a5>] vfs_read+0x95/0x110 > [<c01c1443>] sys_pread64+0x63/0x80 > [<c012146f>] sysenter_do_call+0x12/0x43 > [<ffffffff>] 0xffffffff > > -> #0 (&bb->mutex){--..}: > [<c017d8b7>] validate_chain+0x6b7/0xf50 > [<c017ef2b>] __lock_acquire+0x2cb/0x5b0 > [<c017f299>] lock_acquire+0x89/0xc0 > [<c0d6f2ab>] __mutex_lock_common+0xab/0x3c0 > [<c0d6f698>] mutex_lock_nested+0x38/0x50 > [<c020ba20>] mmap+0x40/0xa0 > [<c01b111e>] mmap_region+0x14e/0x450 > [<c01b170f>] do_mmap_pgoff+0x2ef/0x310 > [<c0125a3d>] sys_mmap2+0xad/0xc0 > [<c012146f>] sysenter_do_call+0x12/0x43 > [<ffffffff>] 0xffffffff > > other info that might help us debug this: > > 1 lock held by X/4873: > #0: (&mm->mmap_sem){----}, at: [<c0125a1e>] sys_mmap2+0x8e/0xc0 > > stack backtrace: > Pid: 4873, comm: X Not tainted 2.6.27-rc6-tip #1 > [<c017cd09>] print_circular_bug_tail+0x79/0xc0 > [<c017d8b7>] validate_chain+0x6b7/0xf50 > [<c017a5b5>] ? trace_hardirqs_off_caller+0x15/0xb0 > [<c017ef2b>] __lock_acquire+0x2cb/0x5b0 > [<c017f299>] lock_acquire+0x89/0xc0 > [<c020ba20>] ? mmap+0x40/0xa0 > [<c0d6f2ab>] __mutex_lock_common+0xab/0x3c0 > [<c020ba20>] ? mmap+0x40/0xa0 > [<c0d6f698>] mutex_lock_nested+0x38/0x50 > [<c020ba20>] ? mmap+0x40/0xa0 > [<c020ba20>] mmap+0x40/0xa0 > [<c01b111e>] mmap_region+0x14e/0x450 > [<c01afb88>] ? arch_get_unmapped_area_topdown+0xf8/0x160 > [<c01b170f>] do_mmap_pgoff+0x2ef/0x310 > [<c0125a3d>] sys_mmap2+0xad/0xc0 > [<c012146f>] sysenter_do_call+0x12/0x43 > [<c0120000>] ? __switch_to+0x130/0x220 > ======================= > evbug.c: Event. Dev: input3, Type: 20, Code: 0, Value: 500 > warning: `sudo' uses deprecated v2 capabilities in a way that may be insecure. > > i've attached the config. > > at first sight it looks like a genuine bug in fs/sysfs/bin.c? Yes, it is a real bug by the looks. bin.c takes bb->mutex under mmap_sem when it is mmapped, and then does its copy_*_user under bb->mutex too. Here is a basic fix for the sysfs lor. From: Nick Piggin <npiggin@suse.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
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