From 34ddaa3e5c0096fef52485186c7eb6cf56ddc686 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 3 Oct 2017 16:39:02 +0200 Subject: [PATCH] powerpc/watchdog: Make use of watchdog_nmi_probe() The rework of the core hotplug code triggers the WARN_ON in start_wd_cpu() on powerpc because it is called multiple times for the boot CPU. The first call is via: start_wd_on_cpu+0x80/0x2f0 watchdog_nmi_reconfigure+0x124/0x170 softlockup_reconfigure_threads+0x110/0x130 lockup_detector_init+0xbc/0xe0 kernel_init_freeable+0x18c/0x37c kernel_init+0x2c/0x160 ret_from_kernel_thread+0x5c/0xbc And then again via the CPU hotplug registration: start_wd_on_cpu+0x80/0x2f0 cpuhp_invoke_callback+0x194/0x620 cpuhp_thread_fun+0x7c/0x1b0 smpboot_thread_fn+0x290/0x2a0 kthread+0x168/0x1b0 ret_from_kernel_thread+0x5c/0xbc This can be avoided by setting up the cpu hotplug state with nocalls and move the initialization to the watchdog_nmi_probe() function. That initializes the hotplug callbacks without invoking the callback and the following core initialization function then configures the watchdog for the online CPUs (in this case CPU0) via softlockup_reconfigure_threads(). Reported-and-tested-by: Michael Ellerman Signed-off-by: Thomas Gleixner Acked-by: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Nicholas Piggin Cc: linuxppc-dev@lists.ozlabs.org --- arch/powerpc/kernel/watchdog.c | 17 ++++++++--------- include/linux/nmi.h | 1 + kernel/watchdog.c | 5 ++++- 3 files changed, 13 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index f9b4c6352d24..c702a8981452 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -373,22 +373,21 @@ void watchdog_nmi_start(void) } /* - * This runs after lockup_detector_init() which sets up watchdog_cpumask. + * Invoked from core watchdog init. */ -static int __init powerpc_watchdog_init(void) +int __init watchdog_nmi_probe(void) { int err; - watchdog_calc_timeouts(); - - err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online", - start_wd_on_cpu, stop_wd_on_cpu); - if (err < 0) + err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, + "powerpc/watchdog:online", + start_wd_on_cpu, stop_wd_on_cpu); + if (err < 0) { pr_warn("Watchdog could not be initialized"); - + return err; + } return 0; } -arch_initcall(powerpc_watchdog_init); static void handle_backtrace_ipi(struct pt_regs *regs) { diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 0c9ed49fb21a..27e249ed7c5c 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -111,6 +111,7 @@ static inline int hardlockup_detector_perf_init(void) { return 0; } void watchdog_nmi_stop(void); void watchdog_nmi_start(void); +int watchdog_nmi_probe(void); /** * touch_nmi_watchdog - restart NMI watchdog timeout. diff --git a/kernel/watchdog.c b/kernel/watchdog.c index fff90fe10007..5c6fb7cd9ae8 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -608,7 +608,6 @@ static inline int watchdog_park_threads(void) { return 0; } static inline void watchdog_unpark_threads(void) { } static inline int watchdog_enable_all_cpus(void) { return 0; } static inline void watchdog_disable_all_cpus(void) { } -static inline void softlockup_init_threads(void) { } static void softlockup_reconfigure_threads(void) { cpus_read_lock(); @@ -617,6 +616,10 @@ static void softlockup_reconfigure_threads(void) watchdog_nmi_start(); cpus_read_unlock(); } +static inline void softlockup_init_threads(void) +{ + softlockup_reconfigure_threads(); +} #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ static void __lockup_detector_cleanup(void)