From: Wu Fengguang <fengguang.wu@intel.com> To: ����ȣ <chanho.min@lge.com> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, "'Jens Axboe'" <axboe@kernel.dk>, "'Andrew Morton'" <akpm@linux-foundation.org> Subject: Re: [PATCH] mm/backing-dev.c: fix crash when USB/SCSI device is detached Date: Mon, 2 Jan 2012 17:57:11 +0800 [thread overview] Message-ID: <20120102095711.GA16570@localhost> (raw) In-Reply-To: <004401ccc932$444a0070$ccde0150$@min@lge.com> On Mon, Jan 02, 2012 at 06:38:21PM +0900, ����ȣ wrote: > from Chanho Min <chanho.min@lge.com> > > System may crash in backing-dev.c when removal SCSI device is detached. > bdi task is killed by bdi_unregister()/'khubd', but task's point remains. > Shortly afterward, If 'wb->wakeup_timer' is expired before > del_timer()/bdi_forker_thread, > wakeup_timer_fn() may wake up the dead thread which cause the crash. > 'bdi->wb.task' should be NULL as this patch. Is it some race condition between del_timer() and del_timer_sync()? bdi_unregister() calls del_timer_sync bdi_wb_shutdown kthread_stop in turn, and del_timer_sync() should guarantee wakeup_timer_fn() is no longer called to access the stopped task. Thanks, Fengguang > Signed-off-by: Chanho Min <chanho.min@lge.com> > --- > mm/backing-dev.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > index 71034f4..4378a5e 100644 > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -607,6 +607,7 @@ static void bdi_wb_shutdown(struct backing_dev_info > *bdi) > if (bdi->wb.task) { > thaw_process(bdi->wb.task); > kthread_stop(bdi->wb.task); > + bdi->wb.task = NULL; > } > } > > -- > 1.7.0.4
WARNING: multiple messages have this Message-ID (diff)
From: Wu Fengguang <fengguang.wu@intel.com> To: ����ȣ <chanho.min@lge.com> Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 'Jens Axboe' <axboe@kernel.dk>, 'Andrew Morton' <akpm@linux-foundation.org> Subject: Re: [PATCH] mm/backing-dev.c: fix crash when USB/SCSI device is detached Date: Mon, 2 Jan 2012 17:57:11 +0800 [thread overview] Message-ID: <20120102095711.GA16570@localhost> (raw) In-Reply-To: <004401ccc932$444a0070$ccde0150$@min@lge.com> On Mon, Jan 02, 2012 at 06:38:21PM +0900, i? 1/2 i? 1/2 i? 1/2 i? 1/2 EGBP wrote: > from Chanho Min <chanho.min@lge.com> > > System may crash in backing-dev.c when removal SCSI device is detached. > bdi task is killed by bdi_unregister()/'khubd', but task's point remains. > Shortly afterward, If 'wb->wakeup_timer' is expired before > del_timer()/bdi_forker_thread, > wakeup_timer_fn() may wake up the dead thread which cause the crash. > 'bdi->wb.task' should be NULL as this patch. Is it some race condition between del_timer() and del_timer_sync()? bdi_unregister() calls del_timer_sync bdi_wb_shutdown kthread_stop in turn, and del_timer_sync() should guarantee wakeup_timer_fn() is no longer called to access the stopped task. Thanks, Fengguang > Signed-off-by: Chanho Min <chanho.min@lge.com> > --- > mm/backing-dev.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > index 71034f4..4378a5e 100644 > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -607,6 +607,7 @@ static void bdi_wb_shutdown(struct backing_dev_info > *bdi) > if (bdi->wb.task) { > thaw_process(bdi->wb.task); > kthread_stop(bdi->wb.task); > + bdi->wb.task = NULL; > } > } > > -- > 1.7.0.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2012-01-02 9:57 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-01-02 9:38 [PATCH] mm/backing-dev.c: fix crash when USB/SCSI device is detached 민찬호 2012-01-02 9:57 ` Wu Fengguang [this message] 2012-01-02 9:57 ` Wu Fengguang 2012-01-03 3:23 ` Chanho Min 2012-01-03 3:23 ` Chanho Min 2012-01-03 4:49 ` Wu Fengguang 2012-01-03 4:49 ` Wu Fengguang 2012-01-03 11:22 ` Chanho Min 2012-01-03 11:22 ` Chanho Min 2012-01-02 9:38 민찬호 2012-01-03 3:47 'Chanho Min' 2012-01-03 3:47 'Chanho Min' 2012-01-05 8:49 Chanho Min 2012-01-15 10:28 ` Rabin Vincent 2012-01-15 12:58 ` Wu Fengguang 2012-01-15 15:41 ` Rabin Vincent 2012-01-16 2:53 ` Wu Fengguang 2012-01-16 5:28 ` Chanho Min 2012-01-16 5:50 ` Wu Fengguang 2012-01-16 5:53 ` Wu Fengguang 2012-01-16 6:34 ` Chanho Min 2012-01-18 19:43 ` Rabin Vincent
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