Re: [PATCH v3 3/4] powerpc/watchdog: use sys_info_with_filter() to avoid duplicate backtraces
From: Petr Mladek <pmladek@suse.com>
Date: 2026-06-26 09:42:23
Also in:
lkml, stable
On Thu 2026-06-25 15:25:57, Bradley Morgan wrote:
quoted hunk ↗ jump to hunk
The powerpc watchdog prints all CPU backtraces itself. When the watchdog mask contains only SYS_INFO_ALL_BT, stripping that bit leaves zero and sys_info(0) falls back to kernel_sys_info. Use sys_info_with_filter() so an explicit all_bt mask does not request the global default.--- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c@@ -418,11 +421,12 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt) xchg(&__wd_nmi_output, 1); // see wd_lockup_ipi + si_mask = READ_ONCE(hardlockup_si_mask); if (sysctl_hardlockup_all_cpu_backtrace || - (hardlockup_si_mask & SYS_INFO_ALL_BT)) + (si_mask & SYS_INFO_ALL_BT)) trigger_allbutcpu_cpu_backtrace(cpu); - sys_info(hardlockup_si_mask & ~SYS_INFO_ALL_BT); + sys_info_with_filter(si_mask, SYS_INFO_ALL_BT); if (hardlockup_panic) nmi_panic(regs, "Hard LOCKUP");
I thought more about it and it is even more complicated. Even if we prevent the duplicated output with sys_info_with_filter() here. Then nmi_panic() might still trigger it once again. We could say that this patch is a step in the right direction and fix the other problem later. But I am not sure. We might need a completely different approach and this is just a step aside. And there is another problem in the panic() code. I am going to comment in it in the 4th patch. Best Regards, Petr