--- /dev/null
+From 51d638b1f56a0bfd9219800620994794a1a2b219 Mon Sep 17 00:00:00 2001
+From: Wanpeng Li <wanpeng.li@hotmail.com>
+Date: Sun, 7 May 2017 00:14:22 -0700
+Subject: block/mq: fix potential deadlock during cpu hotplug
+
+From: Wanpeng Li <wanpeng.li@hotmail.com>
+
+commit 51d638b1f56a0bfd9219800620994794a1a2b219 upstream.
+
+This can be triggered by hot-unplug one cpu.
+
+======================================================
+ [ INFO: possible circular locking dependency detected ]
+ 4.11.0+ #17 Not tainted
+ -------------------------------------------------------
+ step_after_susp/2640 is trying to acquire lock:
+ (all_q_mutex){+.+...}, at: [<ffffffffb33f95b8>] blk_mq_queue_reinit_work+0x18/0x110
+
+ but task is already holding lock:
+ (cpu_hotplug.lock){+.+.+.}, at: [<ffffffffb306d04f>] cpu_hotplug_begin+0x7f/0xe0
+
+ which lock already depends on the new lock.
+
+ the existing dependency chain (in reverse order) is:
+
+ -> #1 (cpu_hotplug.lock){+.+.+.}:
+ lock_acquire+0x11c/0x230
+ __mutex_lock+0x92/0x990
+ mutex_lock_nested+0x1b/0x20
+ get_online_cpus+0x64/0x80
+ blk_mq_init_allocated_queue+0x3a0/0x4e0
+ blk_mq_init_queue+0x3a/0x60
+ loop_add+0xe5/0x280
+ loop_init+0x124/0x177
+ do_one_initcall+0x53/0x1c0
+ kernel_init_freeable+0x1e3/0x27f
+ kernel_init+0xe/0x100
+ ret_from_fork+0x31/0x40
+
+ -> #0 (all_q_mutex){+.+...}:
+ __lock_acquire+0x189a/0x18a0
+ lock_acquire+0x11c/0x230
+ __mutex_lock+0x92/0x990
+ mutex_lock_nested+0x1b/0x20
+ blk_mq_queue_reinit_work+0x18/0x110
+ blk_mq_queue_reinit_dead+0x1c/0x20
+ cpuhp_invoke_callback+0x1f2/0x810
+ cpuhp_down_callbacks+0x42/0x80
+ _cpu_down+0xb2/0xe0
+ freeze_secondary_cpus+0xb6/0x390
+ suspend_devices_and_enter+0x3b3/0xa40
+ pm_suspend+0x129/0x490
+ state_store+0x82/0xf0
+ kobj_attr_store+0xf/0x20
+ sysfs_kf_write+0x45/0x60
+ kernfs_fop_write+0x135/0x1c0
+ __vfs_write+0x37/0x160
+ vfs_write+0xcd/0x1d0
+ SyS_write+0x58/0xc0
+ do_syscall_64+0x8f/0x710
+ return_from_SYSCALL_64+0x0/0x7a
+
+ other info that might help us debug this:
+
+ Possible unsafe locking scenario:
+
+ CPU0 CPU1
+ ---- ----
+ lock(cpu_hotplug.lock);
+ lock(all_q_mutex);
+ lock(cpu_hotplug.lock);
+ lock(all_q_mutex);
+
+ *** DEADLOCK ***
+
+ 8 locks held by step_after_susp/2640:
+ #0: (sb_writers#6){.+.+.+}, at: [<ffffffffb3244aed>] vfs_write+0x1ad/0x1d0
+ #1: (&of->mutex){+.+.+.}, at: [<ffffffffb32d3a51>] kernfs_fop_write+0x101/0x1c0
+ #2: (s_active#166){.+.+.+}, at: [<ffffffffb32d3a59>] kernfs_fop_write+0x109/0x1c0
+ #3: (pm_mutex){+.+...}, at: [<ffffffffb30d2ecd>] pm_suspend+0x21d/0x490
+ #4: (acpi_scan_lock){+.+.+.}, at: [<ffffffffb34dc3d7>] acpi_scan_lock_acquire+0x17/0x20
+ #5: (cpu_add_remove_lock){+.+.+.}, at: [<ffffffffb306d6d7>] freeze_secondary_cpus+0x27/0x390
+ #6: (cpu_hotplug.dep_map){++++++}, at: [<ffffffffb306cfd5>] cpu_hotplug_begin+0x5/0xe0
+ #7: (cpu_hotplug.lock){+.+.+.}, at: [<ffffffffb306d04f>] cpu_hotplug_begin+0x7f/0xe0
+
+ stack backtrace:
+ CPU: 3 PID: 2640 Comm: step_after_susp Not tainted 4.11.0+ #17
+ Hardware name: Dell Inc. OptiPlex 7040/0JCTF8, BIOS 1.4.9 09/12/2016
+ Call Trace:
+ dump_stack+0x99/0xce
+ print_circular_bug+0x1fa/0x270
+ __lock_acquire+0x189a/0x18a0
+ lock_acquire+0x11c/0x230
+ ? lock_acquire+0x11c/0x230
+ ? blk_mq_queue_reinit_work+0x18/0x110
+ ? blk_mq_queue_reinit_work+0x18/0x110
+ __mutex_lock+0x92/0x990
+ ? blk_mq_queue_reinit_work+0x18/0x110
+ ? kmem_cache_free+0x2cb/0x330
+ ? anon_transport_class_unregister+0x20/0x20
+ ? blk_mq_queue_reinit_work+0x110/0x110
+ mutex_lock_nested+0x1b/0x20
+ ? mutex_lock_nested+0x1b/0x20
+ blk_mq_queue_reinit_work+0x18/0x110
+ blk_mq_queue_reinit_dead+0x1c/0x20
+ cpuhp_invoke_callback+0x1f2/0x810
+ ? __flow_cache_shrink+0x160/0x160
+ cpuhp_down_callbacks+0x42/0x80
+ _cpu_down+0xb2/0xe0
+ freeze_secondary_cpus+0xb6/0x390
+ suspend_devices_and_enter+0x3b3/0xa40
+ ? rcu_read_lock_sched_held+0x79/0x80
+ pm_suspend+0x129/0x490
+ state_store+0x82/0xf0
+ kobj_attr_store+0xf/0x20
+ sysfs_kf_write+0x45/0x60
+ kernfs_fop_write+0x135/0x1c0
+ __vfs_write+0x37/0x160
+ ? rcu_read_lock_sched_held+0x79/0x80
+ ? rcu_sync_lockdep_assert+0x2f/0x60
+ ? __sb_start_write+0xd9/0x1c0
+ ? vfs_write+0x1ad/0x1d0
+ vfs_write+0xcd/0x1d0
+ SyS_write+0x58/0xc0
+ ? rcu_read_lock_sched_held+0x79/0x80
+ do_syscall_64+0x8f/0x710
+ ? trace_hardirqs_on_thunk+0x1a/0x1c
+ entry_SYSCALL64_slow_path+0x25/0x25
+
+The cpu hotplug path will hold cpu_hotplug.lock and then reinit all exiting
+queues for blk mq w/ all_q_mutex, however, blk_mq_init_allocated_queue() will
+contend these two locks in the inversion order. This is due to commit eabe06595d62
+(blk/mq: Cure cpu hotplug lock inversion), it fixes a cpu hotplug lock inversion
+issue because of hotplug rework, however the hotplug rework is still work-in-progress
+and lives in a -tip branch and mainline cannot yet trigger that splat. The commit
+breaks the linus's tree in the merge window, so this patch reverts the lock order
+and avoids to splat linus's tree.
+
+Cc: Jens Axboe <axboe@kernel.dk>
+Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
+Cc: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
+Signed-off-by: Jens Axboe <axboe@fb.com>
+Cc: Thierry Escande <thierry.escande@linaro.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ block/blk-mq.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+--- a/block/blk-mq.c
++++ b/block/blk-mq.c
+@@ -2019,15 +2019,15 @@ struct request_queue *blk_mq_init_alloca
+
+ blk_mq_init_cpu_queues(q, set->nr_hw_queues);
+
+- mutex_lock(&all_q_mutex);
+ get_online_cpus();
++ mutex_lock(&all_q_mutex);
+
+ list_add_tail(&q->all_q_node, &all_q_list);
+ blk_mq_add_queue_tag_set(set, q);
+ blk_mq_map_swqueue(q, cpu_online_mask);
+
+- put_online_cpus();
+ mutex_unlock(&all_q_mutex);
++ put_online_cpus();
+
+ return q;
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
