diff options
author | Zach Brown <zach.brown@oracle.com> | 2006-12-30 00:47:02 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@woody.osdl.org> | 2006-12-30 18:55:54 (GMT) |
commit | 1ebb1101c556b1915ff041655e629a072e64dcda (patch) | |
tree | d306821837152a8c772591a9bf136e5e091a7a31 /fs | |
parent | 43cdff92ad47e0ca024c8a07d29f9bb6119e759c (diff) | |
download | linux-1ebb1101c556b1915ff041655e629a072e64dcda.tar.xz |
[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 'fs')
-rw-r--r-- | fs/aio.c | 7 |
1 files changed, 3 insertions, 4 deletions
@@ -599,9 +599,6 @@ static void use_mm(struct mm_struct *mm) * by the calling kernel thread * (Note: this routine is intended to be called only * from a kernel thread context) - * - * Comments: Called with ctx->ctx_lock held. This nests - * task_lock instead ctx_lock. */ static void unuse_mm(struct mm_struct *mm) { @@ -850,14 +847,16 @@ static void aio_kick_handler(struct work_struct *work) { struct kioctx *ctx = container_of(work, struct kioctx, wq.work); mm_segment_t oldfs = get_fs(); + struct mm_struct *mm; int requeue; set_fs(USER_DS); use_mm(ctx->mm); spin_lock_irq(&ctx->ctx_lock); requeue =__aio_run_iocbs(ctx); - unuse_mm(ctx->mm); + mm = ctx->mm; spin_unlock_irq(&ctx->ctx_lock); + unuse_mm(mm); set_fs(oldfs); /* * we're in a worker thread already, don't use queue_delayed_work, |