The patch titled
Subject: watchdog/perf: ensure CPU-bound context when creating hardlockup detector event
has been added to the -mm mm-nonmm-unstable branch. Its filename is
watchdog-perf-ensure-cpu-bound-context-when-creating-hardlockup-detector-event.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/watchdog-perf-ensure-cpu-bound-context-when-creating-hardlockup-detector-event.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Pingfan Liu <kernelfans@xxxxxxxxx>
Subject: watchdog/perf: ensure CPU-bound context when creating hardlockup detector event
Date: Fri, 19 May 2023 10:18:29 -0700
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@xxxxxxxxx>
Co-developed-by: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Signed-off-by: Lecopzer Chen <lecopzer.chen@xxxxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Chen-Yu Tsai <wens@xxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Colin Cross <ccross@xxxxxxxxxxx>
Cc: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Guenter Roeck <groeck@xxxxxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Masayoshi Mizuma <msys.mizuma@xxxxxxxxx>
Cc: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: "Ravi V. Shankar" <ravi.v.shankar@xxxxxxxxx>
Cc: Ricardo Neri <ricardo.neri@xxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Cc: Sumit Garg <sumit.garg@xxxxxxxxxx>
Cc: Tzung-Bi Shih <tzungbi@xxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/watchdog_hld.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/kernel/watchdog_hld.c~watchdog-perf-ensure-cpu-bound-context-when-creating-hardlockup-detector-event
+++ a/kernel/watchdog_hld.c
@@ -165,10 +165,16 @@ static void watchdog_overflow_callback(s
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);
_
Patches currently in -mm which might be from kernelfans@xxxxxxxxx are
watchdog-perf-ensure-cpu-bound-context-when-creating-hardlockup-detector-event.patch
