From 34ddaa3e5c0096fef52485186c7eb6cf56ddc686 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 3 Oct 2017 16:39:02 +0200 Subject: 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 --- include/linux/nmi.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') 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. -- cgit v1.2.3