[kernel/f18] Add patches to fix soft lockup from elevator changes (rhbz 902012)
Josh Boyer
jwboyer at fedoraproject.org
Fri Sep 27 13:26:29 UTC 2013
commit 9827a322e04fb95e55642d59f601c9fe66481a0f
Author: Josh Boyer <jwboyer at fedoraproject.org>
Date: Fri Sep 27 09:22:47 2013 -0400
Add patches to fix soft lockup from elevator changes (rhbz 902012)
...r-Fix-a-race-in-elevator-switching-and-md.patch | 162 ++++++++++++++++++++
...r-acquire-q-sysfs_lock-in-elevator_change.patch | 121 +++++++++++++++
kernel.spec | 11 ++
3 files changed, 294 insertions(+), 0 deletions(-)
---
diff --git a/elevator-Fix-a-race-in-elevator-switching-and-md.patch b/elevator-Fix-a-race-in-elevator-switching-and-md.patch
new file mode 100644
index 0000000..5517687
--- /dev/null
+++ b/elevator-Fix-a-race-in-elevator-switching-and-md.patch
@@ -0,0 +1,162 @@
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+Subject: [PATCH v2 1/2] elevator: Fix a race in elevator switching and md
+ device initialization
+To: linux-kernel at vger.kernel.org
+From: Tomoki Sekiyama <tomoki.sekiyama at hds.com>
+Cc: axboe at kernel.dk, tj at kernel.org, seiji.aguchi at hds.com,
+ vgoyal at redhat.com, majianpeng at gmail.com
+Date: Fri, 30 Aug 2013 18:47:07 -0400
+Message-ID: <20130830224707.21812.63516.stgit at hds.com>
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+The soft lockup below happens at the boot time of the system using dm
+multipath and the udev rules to switch scheduler.
+
+[ 356.127001] BUG: soft lockup - CPU#3 stuck for 22s! [sh:483]
+[ 356.127001] RIP: 0010:[<ffffffff81072a7d>] [<ffffffff81072a7d>] lock_timer_base.isra.35+0x1d/0x50
+...
+[ 356.127001] Call Trace:
+[ 356.127001] [<ffffffff81073810>] try_to_del_timer_sync+0x20/0x70
+[ 356.127001] [<ffffffff8118b08a>] ? kmem_cache_alloc_node_trace+0x20a/0x230
+[ 356.127001] [<ffffffff810738b2>] del_timer_sync+0x52/0x60
+[ 356.127001] [<ffffffff812ece22>] cfq_exit_queue+0x32/0xf0
+[ 356.127001] [<ffffffff812c98df>] elevator_exit+0x2f/0x50
+[ 356.127001] [<ffffffff812c9f21>] elevator_change+0xf1/0x1c0
+[ 356.127001] [<ffffffff812caa50>] elv_iosched_store+0x20/0x50
+[ 356.127001] [<ffffffff812d1d09>] queue_attr_store+0x59/0xb0
+[ 356.127001] [<ffffffff812143f6>] sysfs_write_file+0xc6/0x140
+[ 356.127001] [<ffffffff811a326d>] vfs_write+0xbd/0x1e0
+[ 356.127001] [<ffffffff811a3ca9>] SyS_write+0x49/0xa0
+[ 356.127001] [<ffffffff8164e899>] system_call_fastpath+0x16/0x1b
+
+This is caused by a race between md device initialization by multipathd and
+shell script to switch the scheduler using sysfs.
+
+ - multipathd:
+ SyS_ioctl -> do_vfs_ioctl -> dm_ctl_ioctl -> ctl_ioctl -> table_load
+ -> dm_setup_md_queue -> blk_init_allocated_queue -> elevator_init
+ q->elevator = elevator_alloc(q, e); // not yet initialized
+
+ - sh -c 'echo deadline > /sys/$DEVPATH/queue/scheduler':
+ elevator_switch (in the call trace above)
+ struct elevator_queue *old = q->elevator;
+ q->elevator = elevator_alloc(q, new_e);
+ elevator_exit(old); // lockup! (*)
+
+ - multipathd: (cont.)
+ err = e->ops.elevator_init_fn(q); // init fails; q->elevator is modified
+
+(*) When del_timer_sync() is called, lock_timer_base() will loop infinitely
+while timer->base == NULL. In this case, as timer will never initialized,
+it results in lockup.
+
+This patch introduces acquisition of q->sysfs_lock around elevator_init()
+into blk_init_allocated_queue(), to provide mutual exclusion between
+initialization of the q->scheduler and switching of the scheduler.
+
+This should fix this bugzilla:
+https://bugzilla.redhat.com/show_bug.cgi?id=902012
+
+Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama at hds.com>
+---
+ block/blk-core.c | 10 +++++++++-
+ block/elevator.c | 6 ++++++
+ 2 files changed, 15 insertions(+), 1 deletion(-)
+
+diff --git a/block/blk-core.c b/block/blk-core.c
+index 93a18d1..2f6275f 100644
+--- a/block/blk-core.c
++++ b/block/blk-core.c
+@@ -739,9 +739,17 @@ blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
+
+ q->sg_reserved_size = INT_MAX;
+
++ /* Protect q->elevator from elevator_change */
++ mutex_lock(&q->sysfs_lock);
++
+ /* init elevator */
+- if (elevator_init(q, NULL))
++ if (elevator_init(q, NULL)) {
++ mutex_unlock(&q->sysfs_lock);
+ return NULL;
++ }
++
++ mutex_unlock(&q->sysfs_lock);
++
+ return q;
+ }
+ EXPORT_SYMBOL(blk_init_allocated_queue);
+diff --git a/block/elevator.c b/block/elevator.c
+index 668394d..02d4390 100644
+--- a/block/elevator.c
++++ b/block/elevator.c
+@@ -186,6 +186,12 @@ int elevator_init(struct request_queue *q, char *name)
+ struct elevator_type *e = NULL;
+ int err;
+
++ /*
++ * q->sysfs_lock must be held to provide mutual exclusion between
++ * elevator_switch() and here.
++ */
++ lockdep_assert_held(&q->sysfs_lock);
++
+ if (unlikely(q->elevator))
+ return 0;
+
+
+--
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diff --git a/elevator-acquire-q-sysfs_lock-in-elevator_change.patch b/elevator-acquire-q-sysfs_lock-in-elevator_change.patch
new file mode 100644
index 0000000..6f112b8
--- /dev/null
+++ b/elevator-acquire-q-sysfs_lock-in-elevator_change.patch
@@ -0,0 +1,121 @@
+
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+Subject: [PATCH v2 2/2] elevator: acquire q->sysfs_lock in elevator_change()
+To: linux-kernel at vger.kernel.org
+From: Tomoki Sekiyama <tomoki.sekiyama at hds.com>
+Cc: axboe at kernel.dk, tj at kernel.org, seiji.aguchi at hds.com,
+ vgoyal at redhat.com, majianpeng at gmail.com
+Date: Fri, 30 Aug 2013 18:47:16 -0400
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+
+Add locking of q->sysfs_lock into elevator_change() (an exported function)
+to ensure it is held to protect q->elevator from elevator_init(), even if
+elevator_change() is called from non-sysfs paths.
+sysfs path (elv_iosched_store) uses __elevator_change(), non-locking
+version, as the lock is already taken by elv_iosched_store().
+
+Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama at hds.com>
+---
+ block/elevator.c | 16 ++++++++++++++--
+ 1 file changed, 14 insertions(+), 2 deletions(-)
+
+diff --git a/block/elevator.c b/block/elevator.c
+index 02d4390..6d765f7 100644
+--- a/block/elevator.c
++++ b/block/elevator.c
+@@ -965,7 +965,7 @@ fail_init:
+ /*
+ * Switch this queue to the given IO scheduler.
+ */
+-int elevator_change(struct request_queue *q, const char *name)
++static int __elevator_change(struct request_queue *q, const char *name)
+ {
+ char elevator_name[ELV_NAME_MAX];
+ struct elevator_type *e;
+@@ -987,6 +987,18 @@ int elevator_change(struct request_queue *q, const char *name)
+
+ return elevator_switch(q, e);
+ }
++
++int elevator_change(struct request_queue *q, const char *name)
++{
++ int ret;
++
++ /* Protect q->elevator from elevator_init() */
++ mutex_lock(&q->sysfs_lock);
++ ret = __elevator_change(q, name);
++ mutex_unlock(&q->sysfs_lock);
++
++ return ret;
++}
+ EXPORT_SYMBOL(elevator_change);
+
+ ssize_t elv_iosched_store(struct request_queue *q, const char *name,
+@@ -997,7 +1009,7 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name,
+ if (!q->elevator)
+ return count;
+
+- ret = elevator_change(q, name);
++ ret = __elevator_change(q, name);
+ if (!ret)
+ return count;
+
+
+--
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+the body of a message to majordomo at vger.kernel.org
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diff --git a/kernel.spec b/kernel.spec
index 6c3e98e..35ecf53 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -791,6 +791,10 @@ Patch25105: 0001-HID-kye-Add-report-fixup-for-Genius-Gx-Imperator-Key.patch
#rhbz 971893
Patch25106: bonding-driver-alb-learning.patch
+#rhbz 902012
+Patch25114: elevator-Fix-a-race-in-elevator-switching-and-md.patch
+Patch25115: elevator-acquire-q-sysfs_lock-in-elevator_change.patch
+
# END OF PATCH DEFINITIONS
%endif
@@ -1517,6 +1521,10 @@ ApplyPatch 0001-HID-kye-Add-report-fixup-for-Genius-Gx-Imperator-Key.patch
#rhbz 971893
ApplyPatch bonding-driver-alb-learning.patch
+#rhbz 902012
+ApplyPatch elevator-Fix-a-race-in-elevator-switching-and-md.patch
+ApplyPatch elevator-acquire-q-sysfs_lock-in-elevator_change.patch
+
# END OF PATCH APPLICATIONS
%endif
@@ -2358,6 +2366,9 @@ fi
# ||----w |
# || ||
%changelog
+* Fri Sep 27 2013 Josh Boyer <jwboyer at fedoraproject.org>
+- Add patches to fix soft lockup from elevator changes (rhbz 902012)
+
* Fri Sep 27 2013 Justin M. Forbes <jforbes at fedoraproject.org> 3.10.13-100
- Linux v3.10.13
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