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From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>
Subject: [PATCH v2 1/6] powerpc/watchdog: do not panic from locked CPU's IPI handler
Date: Fri, 29 Sep 2017 13:29:37 +1000	[thread overview]
Message-ID: <20170929032942.4321-2-npiggin@gmail.com> (raw)
In-Reply-To: <20170929032942.4321-1-npiggin@gmail.com>

The SMP watchdog will detect locked CPUs and IPI them to print a
backtrace and registers. If panic on hard lockup is enabled, do
not panic from this handler, because that can cause recursion into
the IPI layer during the panic.

The caller already panics in this case.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/watchdog.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 2f6eadd9408d..532a1adbe89b 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -97,8 +97,7 @@ static void wd_lockup_ipi(struct pt_regs *regs)
 	else
 		dump_stack();
 
-	if (hardlockup_panic)
-		nmi_panic(regs, "Hard LOCKUP");
+	/* Do not panic from here because that can recurse into NMI IPI layer */
 }
 
 static void set_cpumask_stuck(const struct cpumask *cpumask, u64 tb)
-- 
2.13.3

  reply	other threads:[~2017-09-29  3:30 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-29  3:29 [PATCH v2 0/6] More NMI IPI enablement work Nicholas Piggin
2017-09-29  3:29 ` Nicholas Piggin [this message]
2017-10-05  4:21   ` [v2, 1/6] powerpc/watchdog: do not panic from locked CPU's IPI handler Michael Ellerman
2017-09-29  3:29 ` [PATCH v2 2/6] powerpc/watchdog: do not backtrace locked CPUs twice if allcpus backtrace is enabled Nicholas Piggin
2017-09-29  3:29 ` [PATCH v2 3/6] powerpc/watchdog: do not trigger SMP crash from touch_nmi_watchdog Nicholas Piggin
2017-09-29  3:29 ` [PATCH v2 4/6] powerpc/xmon: avoid tripping SMP hardlockup watchdog Nicholas Piggin
2017-09-29  3:29 ` [PATCH v2 5/6] powerpc/64s: Implement system reset idle wakeup reason Nicholas Piggin
2017-09-29  3:29 ` [PATCH v2 6/6] powerpc/powernv: implement NMI IPI with OPAL_SIGNAL_SYSTEM_RESET Nicholas Piggin

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