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SubjectRe: rcu: fix hlist_bl_set_first_rcu annotation
On Fri, Feb 15, 2013 at 12:01:30AM +0000, Andrew Price wrote:
> Hi,
>
> On 03/02/13 18:39, Paul E. McKenney wrote:
> >On Wed, Jan 30, 2013 at 07:07:57PM +0000, Steven Whitehouse wrote:
> >>
> >>Abhi noticed that we were getting a complaint from the RCU subsystem
> >>about access of an RCU protected list under the write side bit lock.
> >>This patch adds additional annotation to check both the RCU read
> >>lock and the write side bit lock before printing a message.
> >>
> >>Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
> >>Reported-by: Abhijith Das <adas@redhat.com>
> >>Tested-by: Abhijith Das <adas@redhat.com>
> >
> >Looks plausible to me on first glance, copying Nick Piggin and Christoph
> >Hellwig. If they have no objections, I will queue this.
> >
> > Thanx, Paul
>
> Has this had any attention yet? I'm also seeing the complaint quite
> frequently:
>
> [ 68.738811] ===============================
> [ 68.741380] [ INFO: suspicious RCU usage. ]
> [ 68.748785] 3.8.0-0.rc7.git1.1.fc19.x86_64 #1 Not tainted
> [ 68.750841] -------------------------------
> [ 68.752418] include/linux/rculist_bl.h:23 suspicious
> rcu_dereference_check() usage!
> [ 68.755264]
> [ 68.755264] other info that might help us debug this:
> [ 68.755264]
> [ 68.758030]
> [ 68.758030] rcu_scheduler_active = 1, debug_locks = 0
> [ 68.760316] 1 lock held by mount/476:
> [ 68.761896] #0: (&type->s_umount_key#38/1){+.+.+.}, at:
> [<ffffffff811dbbee>] sget+0x39e/0x670
> [ 68.767115]
> [ 68.767115] stack backtrace:
> [ 68.769529] Pid: 476, comm: mount Not tainted
> 3.8.0-0.rc7.git1.1.fc19.x86_64 #1
> [ 68.772095] Call Trace:
> [ 68.772995] [<ffffffff810d73b7>] lockdep_rcu_suspicious+0xe7/0x120
> [ 68.775184] [<ffffffffa00e3238>] search_bucket+0x118/0x160 [gfs2]
> [ 68.777559] [<ffffffffa00e47c3>] gfs2_glock_get+0x603/0x7b0 [gfs2]
> [ 68.780749] [<ffffffffa00e41c5>] ? gfs2_glock_get+0x5/0x7b0 [gfs2]
> [ 68.784173] [<ffffffffa00e6db9>] gfs2_glock_nq_num+0x29/0x90 [gfs2]
> [ 68.786551] [<ffffffffa00f2b79>] gfs2_mount+0x869/0xf30 [gfs2]
> [ 68.788672] [<ffffffff810ad428>] ? sched_clock_cpu+0xa8/0x100
> [ 68.790739] [<ffffffff810d561d>] ? trace_hardirqs_off+0xd/0x10
> [ 68.793042] [<ffffffff810ad56f>] ? local_clock+0x5f/0x70
> [ 68.794940] [<ffffffff81702500>] ? __mutex_unlock_slowpath+0x80/0x170
> [ 68.798236] [<ffffffff811dcb49>] mount_fs+0x39/0x1b0
> [ 68.800409] [<ffffffff811879c0>] ? __alloc_percpu+0x10/0x20
> [ 68.803692] [<ffffffff811fa8e3>] vfs_kern_mount+0x63/0xf0
> [ 68.806773] [<ffffffff811fcfb5>] do_mount+0x205/0xa90
> [ 68.809669] [<ffffffff8118c8ec>] ? might_fault+0x5c/0xb0
> [ 68.812717] [<ffffffff811819fb>] ? strndup_user+0x4b/0xf0
> [ 68.816066] [<ffffffff811fd8c3>] sys_mount+0x83/0xc0
> [ 68.818284] [<ffffffff8170ead9>] system_call_fastpath+0x16/0x1b
>
> It would be good to have this silenced for 3.8 but I think there's
> not long to go.

I have queued this, thank you.

3.8 is getting close to the end, but there is always -stable if the 3.8
series is of particular interest for this bug.

Thanx, Paul

> Thanks,
> Andy
>
> >>diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
> >>index 31f9d75..2eb8855 100644
> >>--- a/include/linux/list_bl.h
> >>+++ b/include/linux/list_bl.h
> >>@@ -125,6 +125,11 @@ static inline void hlist_bl_unlock(struct hlist_bl_head *b)
> >> __bit_spin_unlock(0, (unsigned long *)b);
> >> }
> >>
> >>+static inline bool hlist_bl_is_locked(struct hlist_bl_head *b)
> >>+{
> >>+ return bit_spin_is_locked(0, (unsigned long *)b);
> >>+}
> >>+
> >> /**
> >> * hlist_bl_for_each_entry - iterate over list of given type
> >> * @tpos: the type * to use as a loop cursor.
> >>diff --git a/include/linux/rculist_bl.h b/include/linux/rculist_bl.h
> >>index cf1244f..4f216c5 100644
> >>--- a/include/linux/rculist_bl.h
> >>+++ b/include/linux/rculist_bl.h
> >>@@ -20,7 +20,7 @@ static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
> >> static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
> >> {
> >> return (struct hlist_bl_node *)
> >>- ((unsigned long)rcu_dereference(h->first) & ~LIST_BL_LOCKMASK);
> >>+ ((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
> >> }
> >>
> >> /**
> >>
> >>
>



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