[PATCH 1/1] powerpc/watchdog: avoid extra sys_info dumps for all_bt

[Bradley Morgan <include@grrlz.net>]

The powerpc watchdog handles SYS_INFO_ALL_BT itself. When that is the
only hardlockup_sys_info bit, sys_info(0) falls back to kernel_sys_info.

Skip sys_info() for that case.

Fixes: e561383a39ed ("powerpc/watchdog: add support for hardlockup_sys_info sysctl")
Signed-off-by: Bradley Morgan <include@grrlz.net>
---
 arch/powerpc/kernel/watchdog.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index c40c69368476..6338e12651e3 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/arch/powerpc/kernel/watchdog.c
@@ -92,6 +92,16 @@ static cpumask_t wd_smp_cpus_pending;
 static cpumask_t wd_smp_cpus_stuck;
 static u64 wd_smp_last_reset_tb;
 
+static void watchdog_sys_info(unsigned long si_mask)
+{
+	unsigned long dump_mask = si_mask & ~SYS_INFO_ALL_BT;
+
+	if (si_mask && !dump_mask)
+		return;
+
+	sys_info(dump_mask);
+}
+
 #ifdef CONFIG_PPC_PSERIES
 static u64 wd_timeout_pct;
 #endif
@@ -201,6 +211,7 @@ static bool set_cpu_stuck(int cpu)
 static void watchdog_smp_panic(int cpu)
 {
 	static cpumask_t wd_smp_cpus_ipi; // protected by reporting
+	unsigned long si_mask;
 	unsigned long flags;
 	u64 tb, last_reset;
 	int c;
@@ -236,8 +247,9 @@ static void watchdog_smp_panic(int cpu)
 	pr_emerg("CPU %d TB:%lld, last SMP heartbeat TB:%lld (%lldms ago)\n",
 		 cpu, tb, last_reset, tb_to_ns(tb - last_reset) / 1000000);
 
+	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);
 		cpumask_clear(&wd_smp_cpus_ipi);
 	} else {
@@ -251,7 +263,7 @@ static void watchdog_smp_panic(int cpu)
 		}
 	}
 
-	sys_info(hardlockup_si_mask & ~SYS_INFO_ALL_BT);
+	watchdog_sys_info(si_mask);
 	if (hardlockup_panic)
 		nmi_panic(NULL, "Hard LOCKUP");
 
@@ -371,6 +383,7 @@ static void watchdog_timer_interrupt(int cpu)
 
 DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 {
+	unsigned long si_mask;
 	unsigned long flags;
 	int cpu = raw_smp_processor_id();
 	u64 tb;
@@ -418,11 +431,12 @@ 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);
+		watchdog_sys_info(si_mask);
 		if (hardlockup_panic)
 			nmi_panic(regs, "Hard LOCKUP");
 
-- 
2.53.0