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Subject[PATCH v3] x86/acpi: fix a deadlock with cpu hotplug
Date
Similar to the commit 0266d81e9bf5 ("acpi/processor: Prevent cpu hotplug
deadlock") except this is for acpi_processor_ffh_cstate_probe():

"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."

WARNING: possible circular locking dependency detected
------------------------------------------------------
cpuhp/1/15 is trying to acquire lock:
ffffc90003447a28 ((work_completion)(&wfc.work)){+.+.}-{0:0}, at: __flush_work+0x4c6/0x630

but task is already holding lock:
ffffffffafa1c0e8 (cpuidle_lock){+.+.}-{3:3}, at: cpuidle_pause_and_lock+0x17/0x20

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (cpu_hotplug_lock){++++}-{0:0}:
cpus_read_lock+0x3e/0xc0
irq_calc_affinity_vectors+0x5f/0x91
__pci_enable_msix_range+0x10f/0x9a0
pci_alloc_irq_vectors_affinity+0x13e/0x1f0
pci_alloc_irq_vectors_affinity at drivers/pci/msi.c:1208
pqi_ctrl_init+0x72f/0x1618 [smartpqi]
pqi_pci_probe.cold.63+0x882/0x892 [smartpqi]
local_pci_probe+0x7a/0xc0
work_for_cpu_fn+0x2e/0x50
process_one_work+0x57e/0xb90
worker_thread+0x363/0x5b0
kthread+0x1f4/0x220
ret_from_fork+0x27/0x50

-> #0 ((work_completion)(&wfc.work)){+.+.}-{0:0}:
__lock_acquire+0x2244/0x32a0
lock_acquire+0x1a2/0x680
__flush_work+0x4e6/0x630
work_on_cpu+0x114/0x160
acpi_processor_ffh_cstate_probe+0x129/0x250
acpi_processor_evaluate_cst+0x4c8/0x580
acpi_processor_get_power_info+0x86/0x740
acpi_processor_hotplug+0xc3/0x140
acpi_soft_cpu_online+0x102/0x1d0
cpuhp_invoke_callback+0x197/0x1120
cpuhp_thread_fun+0x252/0x2f0
smpboot_thread_fn+0x255/0x440
kthread+0x1f4/0x220
ret_from_fork+0x27/0x50

other info that might help us debug this:

Chain exists of:
(work_completion)(&wfc.work) --> cpuhp_state-up --> cpuidle_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(cpuidle_lock);
lock(cpuhp_state-up);
lock(cpuidle_lock);
lock((work_completion)(&wfc.work));

*** DEADLOCK ***

3 locks held by cpuhp/1/15:
#0: ffffffffaf51ab10 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x69/0x2f0
#1: ffffffffaf51ad40 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x69/0x2f0
#2: ffffffffafa1c0e8 (cpuidle_lock){+.+.}-{3:3}, at: cpuidle_pause_and_lock+0x17/0x20

Call Trace:
dump_stack+0xa0/0xea
print_circular_bug.cold.52+0x147/0x14c
check_noncircular+0x295/0x2d0
__lock_acquire+0x2244/0x32a0
lock_acquire+0x1a2/0x680
__flush_work+0x4e6/0x630
work_on_cpu+0x114/0x160
acpi_processor_ffh_cstate_probe+0x129/0x250
acpi_processor_evaluate_cst+0x4c8/0x580
acpi_processor_get_power_info+0x86/0x740
acpi_processor_hotplug+0xc3/0x140
acpi_soft_cpu_online+0x102/0x1d0
cpuhp_invoke_callback+0x197/0x1120
cpuhp_thread_fun+0x252/0x2f0
smpboot_thread_fn+0x255/0x440
kthread+0x1f4/0x220
ret_from_fork+0x27/0x50

Signed-off-by: Qian Cai <cai@lca.pw>
---

v3:
Remove #ifdef since cstate.o should rather depend on ACPI_PROCESSOR_IDLE
per Rafael.

v2:
Make call_on_cpu() a static inline function to avoid a compilation
error when ACPI_PROCESSOR=m thanks to lkp@intel.com.

arch/x86/kernel/acpi/cstate.c | 3 ++-
drivers/acpi/processor_throttling.c | 7 -------
include/acpi/processor.h | 8 ++++++++
3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index caf2edccbad2..49ae4e1ac9cd 100644
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -161,7 +161,8 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,

/* Make sure we are running on right CPU */

- retval = work_on_cpu(cpu, acpi_processor_ffh_cstate_probe_cpu, cx);
+ retval = call_on_cpu(cpu, acpi_processor_ffh_cstate_probe_cpu, cx,
+ false);
if (retval == 0) {
/* Use the hint in CST */
percpu_entry->states[cx->index].eax = cx->address;
diff --git a/drivers/acpi/processor_throttling.c b/drivers/acpi/processor_throttling.c
index 532a1ae3595a..a0bd56ece3ff 100644
--- a/drivers/acpi/processor_throttling.c
+++ b/drivers/acpi/processor_throttling.c
@@ -897,13 +897,6 @@ static long __acpi_processor_get_throttling(void *data)
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)
diff --git a/include/acpi/processor.h b/include/acpi/processor.h
index 47805172e73d..683e124ad517 100644
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -297,6 +297,14 @@ static inline void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx
}
#endif

+static inline 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);
+}
+
/* in processor_perflib.c */

#ifdef CONFIG_CPU_FREQ
--
2.21.0 (Apple Git-122.2)
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