From: Pingfan Liu <kernelfans@xxxxxxxxx>
hardlockup_detector_event_create() should create perf_event on the
current CPU. Preemption could not get disabled because
perf_event_create_kernel_counter() allocates memory. Instead,
the CPU locality is achieved by processing the code in a per-CPU
bound kthread.
Add a check to prevent mistakes when calling the code in another
code path.
Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Co-developed-by: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Signed-off-by: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>
---
kernel/watchdog_hld.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 701f35f0e2d4..0573cef0b9dc 100644
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -169,10 +169,16 @@ 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;
struct perf_event_attr *wd_attr;
struct perf_event *evt;
+ /*
+ * Preemption is not disabled because memory will be allocated.
+ * Ensure CPU-locality by calling this in per-CPU kthread.
+ */
+ WARN_ON(!is_percpu_thread());
+ cpu = raw_smp_processor_id();
wd_attr = &wd_hw_attr;
wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
--
2.25.1
