watchdog/perf: ensure CPU-bound context when creating hardlockup detector event

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.

Link: https://lkml.kernel.org/r/20230519101840.v5.5.I654063e53782b11d53e736a8ad4897ffd207406a@changeid
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>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Colin Cross <ccross@android.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guenter Roeck <groeck@chromium.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masayoshi Mizuma <msys.mizuma@gmail.com>
Cc: Matthias Kaehlcke <mka@chromium.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Boyd <swboyd@chromium.org>
Cc: Sumit Garg <sumit.garg@linaro.org>
Cc: Tzung-Bi Shih <tzungbi@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 1e8a49d..2125b09 100644 (file)
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -165,10 +165,16 @@ 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);