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[v5,3/6] kernel/watchdog_hld: Ensure CPU-bound context when creating hardlockup detector event

Message ID 20220613135956.15711-4-lecopzer.chen@mediatek.com
State New
Headers show
Series Support hld delayed init based on Pseudo-NMI for | expand

Commit Message

Lecopzer Chen June 13, 2022, 1:59 p.m. UTC 
From: Pingfan Liu <kernelfans@gmail.com>

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@gmail.com>
Co-developed-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
---
 kernel/watchdog_hld.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
diff mbox series

Patch

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);