• Thomas Gleixner's avatar
    powerpc/watchdog: Make use of watchdog_nmi_probe() · 34ddaa3e
    Thomas Gleixner authored
    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: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Acked-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Nicholas Piggin <npiggin@gmail.com>
    Cc: linuxppc-dev@lists.ozlabs.org
    34ddaa3e
watchdog.c 9.49 KB