On Tue, Sep 20, 2005 at 12:23:10PM +0200, Sébastien Dugué wrote:
> what's the point of calling wake_up_locked(&sem->wait) in
> aio_down_wait? We're already in a wakeup path and end up
> calling __wake_up_common recursively.
That's necessary to kick the next semaphore op in the list. The
list_del_init() right above that makes sure that we don't recurse
and run the routine again.
> I think it may be one of the cause of my kernel hanging at the
> very beginning.
>
> When I remove this call things go further but at some point a
> semaphore wait queue gets thrashed and __wake_up_common tries to
> call an invalid callback function.
This patch from Zach might make a difference. Let me know if it changes
the symptoms at all. Sorry if it doesn't apply cleanly, as it is against
a base kernel. Basically, we could sleep while holding ctx_lock, which
does Bad Things(tm) on SMP systems.
-ben
Index: 2.6.13-git12-lock-kiocb/fs/aio.c
===================================================================
--- 2.6.13-git12-lock-kiocb.orig/fs/aio.c
+++ 2.6.13-git12-lock-kiocb/fs/aio.c
@@ -398,7 +398,7 @@ static struct kiocb fastcall *__aio_get_
if (unlikely(!req))
return NULL;
- req->ki_flags = 1 << KIF_LOCKED;
+ req->ki_flags = 0;
req->ki_users = 2;
req->ki_key = 0;
req->ki_ctx = ctx;
@@ -717,6 +717,8 @@ static ssize_t aio_run_iocb(struct kiocb
iocb->ki_run_list.next = iocb->ki_run_list.prev = NULL;
spin_unlock_irq(&ctx->ctx_lock);
+ lock_kiocb(iocb);
+
/* Quit retrying if the i/o has been cancelled */
if (kiocbIsCancelled(iocb)) {
ret = -EINTR;
@@ -781,6 +783,7 @@ out:
aio_queue_work(ctx);
}
}
+ unlock_kiocb(iocb);
return ret;
}
@@ -805,9 +808,7 @@ static int __aio_run_iocbs(struct kioctx
* Hold an extra reference while retrying i/o.
*/
iocb->ki_users++; /* grab extra reference */
- lock_kiocb(iocb);
aio_run_iocb(iocb);
- unlock_kiocb(iocb);
if (__aio_put_req(ctx, iocb)) /* drop extra ref */
put_ioctx(ctx);
}
@@ -1549,7 +1550,6 @@ int fastcall io_submit_one(struct kioctx
spin_lock_irq(&ctx->ctx_lock);
aio_run_iocb(req);
- unlock_kiocb(req);
if (!list_empty(&ctx->run_list)) {
/* drain the run list */
while (__aio_run_iocbs(ctx))
-
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