The patch titled Subject: watchdog: update comments to explain some code has been removed from the -mm tree. Its filename was watchdog-implement-error-handling-for-failure-to-set-up-hardware-perf-events-fix.patch This patch was dropped because it was folded into watchdog-implement-error-handling-for-failure-to-set-up-hardware-perf-events.patch ------------------------------------------------------ From: Don Zickus <dzickus@xxxxxxxxxx> Subject: watchdog: update comments to explain some code This patch was written to update some comments and concerns from Andrew and is expected to be folded into patch watchdog-implement-error-handling-for-failure-to-set-up-hardware-perf-events.patch Resolves: - comments around barriers - comments around blind shutdown of hardware lockup detector - printk letting someone know hardlockup detector is being shut down Signed-off-by: Don Zickus <dzickus@xxxxxxxxxx> Suggested-by: Ulrich Obergfell <uobergfe@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/watchdog.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff -puN kernel/watchdog.c~watchdog-implement-error-handling-for-failure-to-set-up-hardware-perf-events-fix kernel/watchdog.c --- a/kernel/watchdog.c~watchdog-implement-error-handling-for-failure-to-set-up-hardware-perf-events-fix +++ a/kernel/watchdog.c @@ -508,6 +508,12 @@ static void watchdog(unsigned int cpu) * failure path. Check for failures that can occur asynchronously - * for example, when CPUs are on-lined - and shut down the hardware * perf event on each CPU accordingly. + * + * The only non-obvious place this bit can be cleared is through + * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a + * pr_info here would be too noisy as it would result in a message + * every few seconds if the hardlockup was disabled but the softlockup + * enabled. */ if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) watchdog_nmi_disable(cpu); @@ -565,6 +571,9 @@ handle_err: * Disable the hard lockup detector if _any_ CPU fails to set up * set up the hardware perf event. The watchdog() function checks * the NMI_WATCHDOG_ENABLED bit periodically. + * + * The barriers are for syncing up watchdog_enabled across all the + * cpus, as clear_bit() does not use barriers. */ smp_mb__before_atomic(); clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled); @@ -583,6 +592,9 @@ handle_err: else pr_err("disabled (cpu%i): unable to create perf event: %ld\n", cpu, PTR_ERR(event)); + + pr_info("Shutting down hard lockup detector on all cpus\n"); + return PTR_ERR(event); /* success path */ _ Patches currently in -mm which might be from dzickus@xxxxxxxxxx are watchdog-new-definitions-and-variables-initialization.patch watchdog-introduce-the-proc_watchdog_update-function.patch watchdog-move-definition-of-watchdog_proc_mutex-outside-of-proc_dowatchdog.patch watchdog-introduce-the-proc_watchdog_common-function.patch watchdog-introduce-separate-handlers-for-parameters-in-proc-sys-kernel.patch watchdog-implement-error-handling-for-failure-to-set-up-hardware-perf-events.patch watchdog-enable-the-new-user-interface-of-the-watchdog-mechanism.patch watchdog-enable-the-new-user-interface-of-the-watchdog-mechanism-fix.patch watchdog-clean-up-some-function-names-and-arguments.patch watchdog-introduce-the-hardlockup_detector_disable-function.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html