Re: [RFC][PATCH] Fix lock inversion aio_kick_handler()

From: Jeff Moyer
Date: Thu Nov 09 2006 - 17:42:43 EST


==> On Fri, 28 Jul 2006 19:02:23 -0700, Zach Brown <zach.brown@xxxxxxxxxx> said:

Zach> Benjamin LaHaise wrote:
Zach> > On Fri, Jul 28, 2006 at 05:10:32PM -0700, Zach Brown wrote:
Zach> >> Fix lock inversion aio_kick_handler()
Zach> >
Zach> > Doh. Unfortunately, this patch isn't entirely correct as it
Zach> could race with > __put_ioctx() which sets ioctx->mm = NULL.

Zach> Aha, yeah, that's what I was missing. Thanks.

Zach> > Something like the following should do the trick:

Zach> Cool, I'll respin and send it out.

Did you ever resend this patch, Zach? It doesn't appear to be in
current kernels. I'm still running into the lockdep warnings.

-Jeff

--- linux-2.6.19-rc5-mm1/fs/aio.c.orig 2006-11-09 17:28:43.000000000 -0500
+++ linux-2.6.19-rc5-mm1/fs/aio.c 2006-11-09 17:29:29.000000000 -0500
@@ -864,13 +864,15 @@ static void aio_kick_handler(void *data)
struct kioctx *ctx = data;
mm_segment_t oldfs = get_fs();
int requeue;
+ struct mm_struct *mm;

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,
-
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