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authorZach Brown <zach.brown@oracle.com>2006-12-29 16:47:02 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-30 10:55:54 -0800
commit1ebb1101c556b1915ff041655e629a072e64dcda (patch)
treed306821837152a8c772591a9bf136e5e091a7a31 /drivers/scsi/sgiwd93.c
parent43cdff92ad47e0ca024c8a07d29f9bb6119e759c (diff)
[PATCH] Fix lock inversion aio_kick_handler()
lockdep found a AB BC CA lock inversion in retry-based AIO: 1) The task struct's alloc_lock (A) is acquired in process context with interrupts enabled. An interrupt might arrive and call wake_up() which grabs the wait queue's q->lock (B). 2) When performing retry-based AIO the AIO core registers aio_wake_function() as the wake funtion for iocb->ki_wait. It is called with the wait queue's q->lock (B) held and then tries to add the iocb to the run list after acquiring the ctx_lock (C). 3) aio_kick_handler() holds the ctx_lock (C) while acquiring the alloc_lock (A) via lock_task() and unuse_mm(). Lockdep emits a warning saying that we're trying to connect the irq-safe q->lock to the irq-unsafe alloc_lock via ctx_lock. This fixes the inversion by calling unuse_mm() in the AIO kick handing path after we've released the ctx_lock. As Ben LaHaise pointed out __put_ioctx could set ctx->mm to NULL, so we must only access ctx->mm while we have the lock. Signed-off-by: Zach Brown <zach.brown@oracle.com> Signed-off-by: Suparna Bhattacharya <suparna@in.ibm.com> Acked-by: Benjamin LaHaise <bcrl@kvack.org> Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/scsi/sgiwd93.c')
0 files changed, 0 insertions, 0 deletions