[PATCH V2] ACPI/OSL: Replace synchronize_rcu() with call_rcu() in the acpi_os_map_cleanup() to avoid dead lock with cpu hot plug

From: Lan Tianyu
Date: Mon Aug 11 2014 - 23:02:42 EST

When cpu hotplug and evaluating ACPI method happen at the same time,
there is a dead lock between ACPICA namespace lock and cpu hotplug lock.

During cpu hotplug, cpu core will call acpi_cpu_soft_notify() to notify
Linux ACPI under cpu hotplug lock. acpi_cpu_soft_notify() calls
acpi_bus_get_device() to convert ACPI handle to struct acpi_struct.
ACPICA namespace lock will be held in the acpi_bus_get_device().

Evaluating ACPI method may involve in accessing system mem operation
region and the associated address space will be unmapped under
ACPICA namespace lock after accessing. Currently, osl.c uses RCU to
protect io mem pages used by ACPICA. During unmapping, synchronize_rcu()
will be called in the acpi_os_map_cleanup(). Synchronize_rcu() blocks
cpu hotplug via getting cpu hotplug lock. This causes dead lock with
cpu hotplug. Cpu hotplug thread holds cpu hotplug lock first and
then get ACPICA namespace lock. The thread of evaluating ACPI method
does the converse thing. This patch is to replace synchronize_rcu()
with call_rcu() to avoid dead lock. call_rcu() can help to umap address
space asynchronously via provided callback.

Here is dead lock log.
[ 97.149005] INFO: task bash:741 blocked for more than 30 seconds.
[ 97.155914] Not tainted 3.16.0-rc5+ #671
[ 97.160969] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 97.169850] bash D ffff88014e214140 0 741 716 0x00000080
[ 97.177885] ffff88009b9f3a10 0000000000000086 ffff88009dcfb840 ffff88009b9f3fd8
[ 97.186316] 0000000000014140 0000000000014140 ffffffff81c18460 ffffffff81c40fc8
[ 97.194746] ffffffff81c40fcc ffff88009dcfb840 00000000ffffffff ffffffff81c40fd0
[ 97.203175] Call Trace:
[ 97.205946] [<ffffffff817a1b29>] schedule_preempt_disabled+0x29/0x70
[ 97.213246] [<ffffffff817a34fa>] __mutex_lock_slowpath+0xca/0x1c0
[ 97.220258] [<ffffffff817a360f>] mutex_lock+0x1f/0x2f
[ 97.226085] [<ffffffff810bc8cc>] get_online_cpus+0x2c/0x50
[ 97.232408] [<ffffffff8111bbd4>] synchronize_sched_expedited+0x64/0x1c0
[ 97.240011] [<ffffffff8111bb65>] synchronize_sched+0x45/0x50
[ 97.246522] [<ffffffff81431498>] acpi_os_map_cleanup.part.7+0x14/0x3e
[ 97.253928] [<ffffffff81795c54>] acpi_os_unmap_iomem+0xe2/0xea
[ 97.260636] [<ffffffff81795c6a>] acpi_os_unmap_memory+0xe/0x14
[ 97.267355] [<ffffffff814459bc>] acpi_ev_system_memory_region_setup+0x2d/0x97
[ 97.275550] [<ffffffff81459504>] acpi_ut_update_ref_count+0x24d/0x2de
[ 97.282958] [<ffffffff814596af>] acpi_ut_update_object_reference+0x11a/0x18b
[ 97.291055] [<ffffffff81459282>] acpi_ut_remove_reference+0x2e/0x31
[ 97.298265] [<ffffffff8144ffdf>] acpi_ns_detach_object+0x7b/0x80
[ 97.305180] [<ffffffff8144ef11>] acpi_ns_delete_namespace_subtree+0x47/0x81
[ 97.313179] [<ffffffff81440488>] acpi_ds_terminate_control_method+0x85/0x11b
[ 97.321276] [<ffffffff81454625>] acpi_ps_parse_aml+0x164/0x289
[ 97.327988] [<ffffffff81454da6>] acpi_ps_execute_method+0x1c1/0x26c
[ 97.335195] [<ffffffff8144f764>] acpi_ns_evaluate+0x1c1/0x258
[ 97.341814] [<ffffffff81451f86>] acpi_evaluate_object+0x126/0x22f
[ 97.348826] [<ffffffff8144d1ac>] acpi_hw_execute_sleep_method+0x3d/0x68
[ 97.356427] [<ffffffff8144d5cf>] ? acpi_hw_enable_all_runtime_gpes+0x17/0x19
[ 97.364523] [<ffffffff8144deb0>] acpi_hw_legacy_wake+0x4d/0x9d
[ 97.371239] [<ffffffff8144e599>] acpi_hw_sleep_dispatch+0x2a/0x2c
[ 97.378243] [<ffffffff8144e5cb>] acpi_leave_sleep_state+0x17/0x19
[ 97.385252] [<ffffffff8143335c>] acpi_pm_finish+0x3f/0x99
[ 97.391471] [<ffffffff81108c49>] suspend_devices_and_enter+0x139/0x560
[ 97.398972] [<ffffffff81109162>] pm_suspend+0xf2/0x370
[ 97.404900] [<ffffffff81107e69>] state_store+0x79/0xf0
[ 97.410824] [<ffffffff813bc4af>] kobj_attr_store+0xf/0x20
[ 97.417038] [<ffffffff81284f3d>] sysfs_kf_write+0x3d/0x50
[ 97.423260] [<ffffffff81284580>] kernfs_fop_write+0xe0/0x160
[ 97.429776] [<ffffffff81210f47>] vfs_write+0xb7/0x1f0
[ 97.435602] [<ffffffff81211ae6>] SyS_write+0x46/0xb0
[ 97.441334] [<ffffffff8114d986>] ? __audit_syscall_exit+0x1f6/0x2a0
[ 97.448544] [<ffffffff817a4ea9>] system_call_fastpath+0x16/0x1b
[ 97.455361] INFO: task async-enable-no:749 blocked for more than 30 seconds.
[ 97.463353] Not tainted 3.16.0-rc5+ #671
[ 97.468391] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 97.477271] async-enable-no D ffff88014e254140 0 749 2 0x00000080
[ 97.485286] ffff88009de83bf0 0000000000000046 ffff88009b850000 ffff88009de83fd8
[ 97.493714] 0000000000014140 0000000000014140 ffff880148305dc0 ffff880149804160
[ 97.502142] 7fffffffffffffff 0000000000000002 0000000000000000 ffff88009b850000
[ 97.510573] Call Trace:
[ 97.513344] [<ffffffff817a1689>] schedule+0x29/0x70
[ 97.518974] [<ffffffff817a0b49>] schedule_timeout+0x1f9/0x270
[ 97.525588] [<ffffffff81284bfe>] ? __kernfs_create_file+0x7e/0xa0
[ 97.532599] [<ffffffff8128546b>] ? sysfs_add_file_mode_ns+0x9b/0x160
[ 97.539903] [<ffffffff817a36b2>] __down_common+0x93/0xd8
[ 97.546027] [<ffffffff817a376a>] __down_timeout+0x16/0x18
[ 97.552252] [<ffffffff8110546c>] down_timeout+0x4c/0x60
[ 97.558274] [<ffffffff81431f97>] acpi_os_wait_semaphore+0x43/0x57
[ 97.565285] [<ffffffff8145a8f4>] acpi_ut_acquire_mutex+0x48/0x88
[ 97.572200] [<ffffffff81435d1b>] ? acpi_match_device+0x4f/0x4f
[ 97.578918] [<ffffffff8145250f>] acpi_get_data_full+0x3a/0x8e
[ 97.585537] [<ffffffff81435b30>] acpi_bus_get_device+0x23/0x40
[ 97.592253] [<ffffffff8145d839>] acpi_cpu_soft_notify+0x50/0xe6
[ 97.599064] [<ffffffff810e1ddc>] notifier_call_chain+0x4c/0x70
[ 97.605776] [<ffffffff810e1eee>] __raw_notifier_call_chain+0xe/0x10
[ 97.612983] [<ffffffff810bc993>] cpu_notify+0x23/0x50
[ 97.618815] [<ffffffff810bcb98>] _cpu_up+0x168/0x180
[ 97.624542] [<ffffffff810bcc5c>] _cpu_up_with_trace+0x2c/0xe0
[ 97.631153] [<ffffffff810bd050>] ? disable_nonboot_cpus+0x1c0/0x1c0
[ 97.638360] [<ffffffff810bd06f>] async_enable_nonboot_cpus+0x1f/0x70
[ 97.645670] [<ffffffff810dda02>] kthread+0xd2/0xf0
[ 97.651201] [<ffffffff810dd930>] ? insert_kthread_work+0x40/0x40
[ 97.658117] [<ffffffff817a4dfc>] ret_from_fork+0x7c/0xb0

Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
---
drivers/acpi/osl.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index bad25b0..d8674ab 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -94,6 +94,7 @@ struct acpi_ioremap {
acpi_physical_address phys;
acpi_size size;
unsigned long refcount;
+ struct rcu_head rcu;
};

static LIST_HEAD(acpi_ioremaps);
@@ -421,13 +422,18 @@ static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
list_del_rcu(&map->list);
}

+static void acpi_os_map_reclaim(struct rcu_head *rcu)
+{
+ struct acpi_ioremap *map = container_of(rcu, struct acpi_ioremap, rcu);
+
+ acpi_unmap(map->phys, map->virt);
+ kfree(map);
+}
+
static void acpi_os_map_cleanup(struct acpi_ioremap *map)
{
- if (!map->refcount) {
- synchronize_rcu();
- acpi_unmap(map->phys, map->virt);
- kfree(map);
- }
+ if (!map->refcount)
+ call_rcu(&map->rcu, acpi_os_map_reclaim);
}

void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size)
--
1.8.4.rc0.1.g8f6a3e5.dirty

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