On 25/11/2021, 11:33:46, Nicholas Piggin wrote:
> wd_smp_last_reset_tb now gets reset by watchdog_smp_panic() as part of
> marking CPUs stuck and removing them from the pending mask before it
> begins any printing. This causes last reset times reported to be off.
>
> Fix this by reading it into a local variable before it gets reset.
>
> Fixes: 76521c4b0291 ("powerpc/watchdog: Avoid holding wd_smp_lock over printk
> and smp_send_nmi_ipi")
> Signed-off-by: Nicholas Piggin <[email protected]>
> ---
>
> This is the delta for patches 1-4 between v3 and v4 of the series which
> is the result of fixing the bug in patch 3. Sending because v3 got
> merged into powerpc next
What about the 5th patch in the v4 series titled "[PATCH v4 5/5]
powerpc/watchdog: help remote CPUs to flush NMI printk output"?
> Thanks,
> Nick
>
> arch/powerpc/kernel/watchdog.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
> index b6533539386b..23745af38d62 100644
> --- a/arch/powerpc/kernel/watchdog.c
> +++ b/arch/powerpc/kernel/watchdog.c
> @@ -179,13 +179,14 @@ static void watchdog_smp_panic(int cpu)
> {
> static cpumask_t wd_smp_cpus_ipi; // protected by reporting
> unsigned long flags;
> - u64 tb;
> + u64 tb, last_reset;
> int c;
>
> wd_smp_lock(&flags);
> /* Double check some things under lock */
> tb = get_tb();
> - if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb)
> + last_reset = wd_smp_last_reset_tb;
> + if ((s64)(tb - last_reset) < (s64)wd_smp_panic_timeout_tb)
> goto out;
> if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
> goto out;
> @@ -210,8 +211,7 @@ static void watchdog_smp_panic(int cpu)
> pr_emerg("CPU %d detected hard LOCKUP on other CPUs %*pbl\n",
> cpu, cpumask_pr_args(&wd_smp_cpus_ipi));
> pr_emerg("CPU %d TB:%lld, last SMP heartbeat TB:%lld (%lldms ago)\n",
> - cpu, tb, wd_smp_last_reset_tb,
> - tb_to_ns(tb - wd_smp_last_reset_tb) / 1000000);
> + cpu, tb, last_reset, tb_to_ns(tb - last_reset) / 1000000);
>
> if (!sysctl_hardlockup_all_cpu_backtrace) {
> /*
>
