With the enhanced CPU hotplug lockdep coverage the following lockdep splat
happens:
======================================================
WARNING: possible circular locking dependency detected
4.12.0-rc2+ #84 Tainted: G W
------------------------------------------------------
cpuhp/1/15 is trying to acquire lock:
flush_work+0x39/0x2f0
but task is already holding lock:
cpuhp_thread_fun+0x30/0x160
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (cpuhp_state){+.+.+.}:
lock_acquire+0xb4/0x200
cpuhp_kick_ap_work+0x72/0x330
_cpu_down+0x8b/0x100
do_cpu_down+0x3e/0x60
cpu_down+0x10/0x20
cpu_subsys_offline+0x14/0x20
device_offline+0x88/0xb0
online_store+0x4c/0xa0
dev_attr_store+0x18/0x30
sysfs_kf_write+0x45/0x60
kernfs_fop_write+0x156/0x1e0
__vfs_write+0x37/0x160
vfs_write+0xca/0x1c0
SyS_write+0x58/0xc0
entry_SYSCALL_64_fastpath+0x23/0xc2
-> #1 (cpu_hotplug_lock.rw_sem){++++++}:
lock_acquire+0xb4/0x200
cpus_read_lock+0x3d/0xb0
apply_workqueue_attrs+0x17/0x50
__alloc_workqueue_key+0x1e1/0x530
scsi_host_alloc+0x373/0x480 [scsi_mod]
ata_scsi_add_hosts+0xcb/0x130 [libata]
ata_host_register+0x11a/0x2c0 [libata]
ata_host_activate+0xf0/0x150 [libata]
ahci_host_activate+0x13e/0x170 [libahci]
ahci_init_one+0xa3a/0xd3f [ahci]
local_pci_probe+0x45/0xa0
work_for_cpu_fn+0x14/0x20
process_one_work+0x1f9/0x690
worker_thread+0x200/0x3d0
kthread+0x138/0x170
ret_from_fork+0x31/0x40
-> #0 ((&wfc.work)){+.+.+.}:
__lock_acquire+0x11e1/0x13e0
lock_acquire+0xb4/0x200
flush_work+0x5c/0x2f0
work_on_cpu+0xa1/0xd0
acpi_processor_get_throttling+0x3d/0x50
acpi_processor_reevaluate_tstate+0x2c/0x50
acpi_soft_cpu_online+0x69/0xd0
cpuhp_invoke_callback+0xb4/0x8b0
cpuhp_up_callbacks+0x36/0xc0
cpuhp_thread_fun+0x14e/0x160
smpboot_thread_fn+0x1e8/0x300
kthread+0x138/0x170
ret_from_fork+0x31/0x40
other info that might help us debug this:
Chain exists of:
(&wfc.work) --> cpu_hotplug_lock.rw_sem --> cpuhp_state
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(cpuhp_state);
lock(cpu_hotplug_lock.rw_sem);
lock(cpuhp_state);
lock((&wfc.work));
*** DEADLOCK ***
1 lock held by cpuhp/1/15:
cpuhp_thread_fun+0x30/0x160
stack backtrace:
CPU: 1 PID: 15 Comm: cpuhp/1 Tainted: G W 4.12.0-rc2+ #84
Hardware name: Supermicro SYS-4048B-TR4FT/X10QBi, BIOS 1.1a 07/29/2015
Call Trace:
dump_stack+0x85/0xc4
print_circular_bug+0x209/0x217
__lock_acquire+0x11e1/0x13e0
lock_acquire+0xb4/0x200
? lock_acquire+0xb4/0x200
? flush_work+0x39/0x2f0
? acpi_processor_start+0x50/0x50
flush_work+0x5c/0x2f0
? flush_work+0x39/0x2f0
? acpi_processor_start+0x50/0x50
? mark_held_locks+0x6d/0x90
? queue_work_on+0x56/0x90
? trace_hardirqs_on_caller+0x154/0x1c0
? trace_hardirqs_on+0xd/0x10
? acpi_processor_start+0x50/0x50
work_on_cpu+0xa1/0xd0
? find_worker_executing_work+0x50/0x50
? acpi_processor_power_exit+0x70/0x70
acpi_processor_get_throttling+0x3d/0x50
acpi_processor_reevaluate_tstate+0x2c/0x50
acpi_soft_cpu_online+0x69/0xd0
cpuhp_invoke_callback+0xb4/0x8b0
? lock_acquire+0xb4/0x200
? padata_replace+0x120/0x120
cpuhp_up_callbacks+0x36/0xc0
cpuhp_thread_fun+0x14e/0x160
smpboot_thread_fn+0x1e8/0x300
kthread+0x138/0x170
? sort_range+0x30/0x30
? kthread_create_on_node+0x70/0x70
ret_from_fork+0x31/0x40
The problem is that the work is scheduled on the current CPU from the
hotplug thread associated with that CPU.
It's not required to invoke these functions via the workqueue because the
hotplug thread runs on the target CPU already.
Check whether current is a per cpu thread pinned on the target CPU and
invoke the function directly to avoid the workqueue.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: linux-acpi@xxxxxxxxxxxxxxx
---
drivers/acpi/processor_throttling.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
--- a/drivers/acpi/processor_throttling.c
+++ b/drivers/acpi/processor_throttling.c
@@ -909,6 +909,13 @@ static long __acpi_processor_get_throttl
return pr->throttling.acpi_processor_get_throttling(pr);
}
+static int call_on_cpu(int cpu, long (*fn)(void *), void *arg, bool direct)
+{
+ if (direct || (is_percpu_thread() && cpu == smp_processor_id()))
+ return fn(arg);
+ return work_on_cpu(cpu, fn, arg);
+}
+
static int acpi_processor_get_throttling(struct acpi_processor *pr)
{
if (!pr)
@@ -926,7 +933,7 @@ static int acpi_processor_get_throttling
if (!cpu_online(pr->id))
return -ENODEV;
- return work_on_cpu(pr->id, __acpi_processor_get_throttling, pr);
+ return call_on_cpu(pr->id, __acpi_processor_get_throttling, pr, false);
}
static int acpi_processor_get_fadt_info(struct acpi_processor *pr)
@@ -1076,13 +1083,6 @@ static long acpi_processor_throttling_fn
arg->target_state, arg->force);
}
-static int call_on_cpu(int cpu, long (*fn)(void *), void *arg, bool direct)
-{
- if (direct)
- return fn(arg);
- return work_on_cpu(cpu, fn, arg);
-}
-
static int __acpi_processor_set_throttling(struct acpi_processor *pr,
int state, bool force, bool direct)
{
--
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