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Subject[PATCH] kernel/watchdog_hld.c: Fix access percpu in preemptible context
Date
commit 367c820ef08082 ("arm64: Enable perf events based hard lockup detector")
reinitilizes lockup detector after arm64 PMU is initialized and provide
another chance for access smp_processor_id() in preemptible context.
Since hardlockup_detector_event_create() use many percpu relative variable,
just try to fix this by get/put_cpu()

BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
caller is debug_smp_processor_id+0x20/0x2c
CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.10.0+ #276
Hardware name: linux,dummy-virt (DT)
Call trace:
dump_backtrace+0x0/0x3c0
show_stack+0x20/0x6c
dump_stack+0x2f0/0x42c
check_preemption_disabled+0x1cc/0x1dc
debug_smp_processor_id+0x20/0x2c
hardlockup_detector_event_create+0x34/0x18c
hardlockup_detector_perf_init+0x2c/0x134
watchdog_nmi_probe+0x18/0x24
lockup_detector_init+0x44/0xa8
armv8_pmu_driver_init+0x54/0x78
do_one_initcall+0x184/0x43c
kernel_init_freeable+0x368/0x380
kernel_init+0x1c/0x1cc
ret_from_fork+0x10/0x30


Fixes: 367c820ef08082 ("arm64: Enable perf events based hard lockup detector")
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Sumit Garg <sumit.garg@linaro.org>

---
kernel/watchdog_hld.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 247bf0b1582c..c591a1ea8eb3 100644
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -165,7 +165,7 @@ static void watchdog_overflow_callback(struct perf_event *event,

static int hardlockup_detector_event_create(void)
{
- unsigned int cpu = smp_processor_id();
+ unsigned int cpu = get_cpu();
struct perf_event_attr *wd_attr;
struct perf_event *evt;

@@ -176,11 +176,13 @@ static int hardlockup_detector_event_create(void)
evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL,
watchdog_overflow_callback, NULL);
if (IS_ERR(evt)) {
+ put_cpu();
pr_debug("Perf event create on CPU %d failed with %ld\n", cpu,
PTR_ERR(evt));
return PTR_ERR(evt);
}
this_cpu_write(watchdog_ev, evt);
+ put_cpu();
return 0;
}

--
2.25.1
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