On 2 October 2026 14:10:27 BST, Qiliang Yuan <[email protected]> wrote: >The watchdog is initialized at boot to run on all housekeeping CPUs >(HK_TYPE_KERNEL_NOISE). When a cpuset isolated partition removes CPUs >from that mask at runtime, watchdog continues running on those CPUs >because nothing updates watchdog_cpumask. > >Save the boot-time watchdog_cpumask as watchdog_cpumask_boot, which >captures the user's intended coverage (possibly narrowed via kernel >parameter or sysctl) before any runtime isolation. Introduce >lockup_detector_hk_update() which intersects this boot snapshot with >the current HK_TYPE_KERNEL_NOISE mask and reconfigures the detector. >This ensures that isolated CPUs are excluded while honoring any >manual narrowing the admin applied at or after boot. > >lockup_detector_hk_update() snapshots the RCU-protected housekeeping >mask under rcu_read_lock(), then updates watchdog_cpumask and calls >__lockup_detector_reconfigure() under watchdog_mutex, matching the >same locking discipline used by proc_watchdog_cpumask(). >
Added Petr mladek, maybe he may be interested? See comments: >Signed-off-by: Qiliang Yuan <[email protected]> >--- > include/linux/nmi.h | 2 ++ > kernel/watchdog.c | 24 ++++++++++++++++++++++++ > 2 files changed, 26 insertions(+) > >diff --git a/include/linux/nmi.h b/include/linux/nmi.h >index af69712df5f48..409af7884d939 100644 >--- a/include/linux/nmi.h >+++ b/include/linux/nmi.h >@@ -37,6 +37,7 @@ extern int sysctl_hardlockup_all_cpu_backtrace; > static inline void lockup_detector_init(void) { } > static inline void lockup_detector_retry_init(void) { } > static inline void lockup_detector_soft_poweroff(void) { } >+static inline void lockup_detector_hk_update(void) { } > #endif /* !CONFIG_LOCKUP_DETECTOR */ > > #ifdef CONFIG_SOFTLOCKUP_DETECTOR >@@ -120,6 +121,7 @@ void watchdog_hardlockup_enable(unsigned int cpu); > void watchdog_hardlockup_disable(unsigned int cpu); > > void lockup_detector_reconfigure(void); >+void lockup_detector_hk_update(void); > > #ifdef CONFIG_HARDLOCKUP_DETECTOR_BUDDY > void watchdog_buddy_check_hardlockup(int hrtimer_interrupts); >diff --git a/kernel/watchdog.c b/kernel/watchdog.c >index e567fbb0d4692..d4eccb8e337f1 100644 >--- a/kernel/watchdog.c >+++ b/kernel/watchdog.c >@@ -53,6 +53,8 @@ static int __read_mostly watchdog_hardlockup_available; > > struct cpumask watchdog_cpumask __read_mostly; > unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask); >+/* Boot snapshot: user's intended watchdog mask before any runtime isolation. >*/ >+static struct cpumask watchdog_cpumask_boot __ro_after_init; > > #ifdef CONFIG_HARDLOCKUP_DETECTOR > >@@ -1348,6 +1350,27 @@ static void __init lockup_detector_delay_init(struct >work_struct *work) > lockup_detector_setup(); > } > Why no comment?, other than that, Looks good to me, cheerss Reviewed-by: Bradley Morgan <[email protected]> >+void lockup_detector_hk_update(void) >+{ >+ cpumask_var_t new_mask; >+ >+ if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) >+ return; >+ >+ rcu_read_lock(); >+ cpumask_and(new_mask, &watchdog_cpumask_boot, >+ housekeeping_cpumask_rcu(HK_TYPE_KERNEL_NOISE)); >+ rcu_read_unlock(); >+ >+ mutex_lock(&watchdog_mutex); >+ cpumask_copy(&watchdog_cpumask, new_mask); >+ __lockup_detector_reconfigure(false); >+ mutex_unlock(&watchdog_mutex); >+ >+ free_cpumask_var(new_mask); >+} >+EXPORT_SYMBOL_GPL(lockup_detector_hk_update); >+ > /* > * lockup_detector_retry_init - retry init lockup detector if possible. > * >@@ -1390,6 +1413,7 @@ void __init lockup_detector_init(void) > > cpumask_copy(&watchdog_cpumask, > housekeeping_cpumask(HK_TYPE_KERNEL_NOISE)); >+ cpumask_copy(&watchdog_cpumask_boot, &watchdog_cpumask); > > if (!watchdog_hardlockup_probe()) > watchdog_hardlockup_available = true; > > --- Thanks! "I'm not a very positive person" - Linus torvalds
