Re: [PATCH] ACPI/OSL: Remove RCU in the osl.c to avoid dead lock with cpu hot plug
From: Rafael J. Wysocki
Date: Tue Aug 05 2014 - 21:05:46 EST
On Monday, August 04, 2014 04:40:08 PM Lan Tianyu wrote:
> 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(). Synchroize_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 fix it via replacing
> RCU with spin lock.
>
> 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 | 60 +++++++++++++++++++++++++++++-------------------------
> 1 file changed, 32 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index bad25b0..d018d95 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -97,7 +97,7 @@ struct acpi_ioremap {
> };
>
> static LIST_HEAD(acpi_ioremaps);
> -static DEFINE_MUTEX(acpi_ioremap_lock);
> +static DEFINE_SPINLOCK(acpi_ioremap_lock);
>
> static void __init acpi_osi_setup_late(void);
>
> @@ -267,13 +267,13 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
> }
> }
>
> -/* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */
> +/* Must be called with 'acpi_ioremap_lock'. */
> static struct acpi_ioremap *
> acpi_map_lookup(acpi_physical_address phys, acpi_size size)
> {
> struct acpi_ioremap *map;
>
> - list_for_each_entry_rcu(map, &acpi_ioremaps, list)
> + list_for_each_entry(map, &acpi_ioremaps, list)
> if (map->phys <= phys &&
> phys + size <= map->phys + map->size)
> return map;
> @@ -281,7 +281,7 @@ acpi_map_lookup(acpi_physical_address phys, acpi_size size)
> return NULL;
> }
>
> -/* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */
> +/* Must be called with 'acpi_ioremap_lock'. */
> static void __iomem *
> acpi_map_vaddr_lookup(acpi_physical_address phys, unsigned int size)
> {
> @@ -298,29 +298,29 @@ void __iomem *acpi_os_get_iomem(acpi_physical_address phys, unsigned int size)
> {
> struct acpi_ioremap *map;
> void __iomem *virt = NULL;
> + unsigned long flags;
>
> - mutex_lock(&acpi_ioremap_lock);
> + spin_lock_irqsave(&acpi_ioremap_lock, flags);
Why do you need to do _irqsave here? It was a mutex before, after all,
so it can't be called from interrupt context.
In other places below too.
> map = acpi_map_lookup(phys, size);
> if (map) {
> virt = map->virt + (phys - map->phys);
> map->refcount++;
> }
> - mutex_unlock(&acpi_ioremap_lock);
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
> return virt;
> }
> EXPORT_SYMBOL_GPL(acpi_os_get_iomem);
>
> -/* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */
> +/* Must be called with 'acpi_ioremap_lock'. */
> static struct acpi_ioremap *
> acpi_map_lookup_virt(void __iomem *virt, acpi_size size)
> {
> struct acpi_ioremap *map;
>
> - list_for_each_entry_rcu(map, &acpi_ioremaps, list)
> + list_for_each_entry(map, &acpi_ioremaps, list)
> if (map->virt <= virt &&
> virt + size <= map->virt + map->size)
> return map;
> -
> return NULL;
> }
>
> @@ -362,6 +362,7 @@ acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)
> void __iomem *virt;
> acpi_physical_address pg_off;
> acpi_size pg_sz;
> + unsigned long flags;
>
> if (phys > ULONG_MAX) {
> printk(KERN_ERR PREFIX "Cannot map memory that high\n");
> @@ -371,7 +372,7 @@ acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)
> if (!acpi_gbl_permanent_mmap)
> return __acpi_map_table((unsigned long)phys, size);
>
> - mutex_lock(&acpi_ioremap_lock);
> + spin_lock_irqsave(&acpi_ioremap_lock, flags);
> /* Check if there's a suitable mapping already. */
> map = acpi_map_lookup(phys, size);
> if (map) {
> @@ -381,7 +382,7 @@ acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)
>
> map = kzalloc(sizeof(*map), GFP_KERNEL);
> if (!map) {
> - mutex_unlock(&acpi_ioremap_lock);
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
> return NULL;
> }
>
> @@ -389,7 +390,7 @@ acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)
> pg_sz = round_up(phys + size, PAGE_SIZE) - pg_off;
> virt = acpi_map(pg_off, pg_sz);
> if (!virt) {
> - mutex_unlock(&acpi_ioremap_lock);
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
> kfree(map);
> return NULL;
> }
> @@ -400,10 +401,10 @@ acpi_os_map_iomem(acpi_physical_address phys, acpi_size size)
> map->size = pg_sz;
> map->refcount = 1;
>
> - list_add_tail_rcu(&map->list, &acpi_ioremaps);
> + list_add_tail(&map->list, &acpi_ioremaps);
>
> out:
> - mutex_unlock(&acpi_ioremap_lock);
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
> return map->virt + (phys - map->phys);
> }
> EXPORT_SYMBOL_GPL(acpi_os_map_iomem);
> @@ -418,13 +419,12 @@ EXPORT_SYMBOL_GPL(acpi_os_map_memory);
> static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
> {
> if (!--map->refcount)
> - list_del_rcu(&map->list);
> + list_del(&map->list);
> }
>
> static void acpi_os_map_cleanup(struct acpi_ioremap *map)
> {
> if (!map->refcount) {
> - synchronize_rcu();
> acpi_unmap(map->phys, map->virt);
> kfree(map);
> }
> @@ -433,21 +433,22 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map)
> void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size)
> {
> struct acpi_ioremap *map;
> + unsigned long flags;
>
> if (!acpi_gbl_permanent_mmap) {
> __acpi_unmap_table(virt, size);
> return;
> }
>
> - mutex_lock(&acpi_ioremap_lock);
> + spin_lock_irqsave(&acpi_ioremap_lock, flags);
> map = acpi_map_lookup_virt(virt, size);
> if (!map) {
> - mutex_unlock(&acpi_ioremap_lock);
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
> WARN(true, PREFIX "%s: bad address %p\n", __func__, virt);
> return;
> }
> acpi_os_drop_map_ref(map);
> - mutex_unlock(&acpi_ioremap_lock);
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
>
> acpi_os_map_cleanup(map);
> }
> @@ -490,6 +491,7 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
> {
> u64 addr;
> struct acpi_ioremap *map;
> + unsigned long flags;
>
> if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
> return;
> @@ -499,14 +501,14 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
> if (!addr || !gas->bit_width)
> return;
>
> - mutex_lock(&acpi_ioremap_lock);
> + spin_lock_irqsave(&acpi_ioremap_lock, flags);
> map = acpi_map_lookup(addr, gas->bit_width / 8);
> if (!map) {
> - mutex_unlock(&acpi_ioremap_lock);
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
> return;
> }
> acpi_os_drop_map_ref(map);
> - mutex_unlock(&acpi_ioremap_lock);
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
>
> acpi_os_map_cleanup(map);
> }
> @@ -939,11 +941,12 @@ acpi_os_read_memory(acpi_physical_address phys_addr, u64 *value, u32 width)
> unsigned int size = width / 8;
> bool unmap = false;
> u64 dummy;
> + unsigned long flags;
>
> - rcu_read_lock();
> + spin_lock_irqsave(&acpi_ioremap_lock, flags);
> virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
> if (!virt_addr) {
> - rcu_read_unlock();
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
> virt_addr = acpi_os_ioremap(phys_addr, size);
> if (!virt_addr)
> return AE_BAD_ADDRESS;
> @@ -973,7 +976,7 @@ acpi_os_read_memory(acpi_physical_address phys_addr, u64 *value, u32 width)
> if (unmap)
> iounmap(virt_addr);
> else
> - rcu_read_unlock();
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
>
> return AE_OK;
> }
> @@ -997,11 +1000,12 @@ acpi_os_write_memory(acpi_physical_address phys_addr, u64 value, u32 width)
> void __iomem *virt_addr;
> unsigned int size = width / 8;
> bool unmap = false;
> + unsigned long flags;
>
> - rcu_read_lock();
> + spin_lock_irqsave(&acpi_ioremap_lock, flags);
> virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
> if (!virt_addr) {
> - rcu_read_unlock();
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
> virt_addr = acpi_os_ioremap(phys_addr, size);
> if (!virt_addr)
> return AE_BAD_ADDRESS;
> @@ -1028,7 +1032,7 @@ acpi_os_write_memory(acpi_physical_address phys_addr, u64 value, u32 width)
> if (unmap)
> iounmap(virt_addr);
> else
> - rcu_read_unlock();
> + spin_unlock_irqrestore(&acpi_ioremap_lock, flags);
>
> return AE_OK;
> }
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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