Hi Doug,
On Wed, Aug 21, 2024 at 02:53:57PM -0700, Douglas Anderson wrote:
> When testing hard lockup handling on my sc7180-trogdor-lazor device
> with pseudo-NMI enabled, with serial console enabled and with kgdb
> disabled, I found that the stack crawls printed to the serial console
> ended up as a jumbled mess. After rebooting, the pstore-based console
> looked fine though. Also, enabling kgdb to trap the panic made the
> console look fine and avoided the mess.
Just a small nit:
> while (num_other_online_cpus() && timeout--)
> udelay(1);
>
> - if (num_other_online_cpus())
> + /*
> + * If CPUs are still online, try an NMI. There's no excuse for this to
> + * be slow, so we only give them an extra 10 ms to respond.
> + */
> + if (num_other_online_cpus() && ipi_should_be_nmi(IPI_CPU_STOP_NMI)) {
We probably want an smp_rmb() here...
> + cpumask_copy(&mask, cpu_online_mask);
> + cpumask_clear_cpu(smp_processor_id(), &mask);
> +
> + pr_info("SMP: retry stop with NMI for CPUs %*pbl\n",
> + cpumask_pr_args(&mask));
> +
> + smp_cross_call(&mask, IPI_CPU_STOP_NMI);
> + timeout = USEC_PER_MSEC * 10;
> + while (num_other_online_cpus() && timeout--)
> + udelay(1);
> + }
> +
> + if (num_other_online_cpus()) {
... and again here, just to make sure that the re-read of cpu_online_mask
is ordered after the read of __num_online_cpus in num_other_online_cpus().
I can add those when applying.
Will
