Subject: [PATCH 1/5] powerpc/watchdog: do not panic from locked CPU's IPI handler

From: Nicholas Piggin <[email-masked]>
Date: Mon, 18 Sep 2017 18:27:02 +1000

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 <[email-masked]>
---
 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