[PATCH v3 2/4] watchdog: use sys_info_with_filter() to avoid duplicate backtraces

[Bradley Morgan]

The 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.

Fixes: a9af76a78760 ("watchdog: add sys_info sysctls to dump sys info on system 
lockup")
Cc: sta...@vger.kernel.org
Signed-off-by: Bradley Morgan <incl...@grrlz.net>
---
 kernel/watchdog.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 87dd5e0f6968..ff284593cb90 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -208,6 +208,7 @@ void watchdog_hardlockup_check(unsigned int cpu, struct 
pt_regs *regs)
 {
        int hardlockup_all_cpu_backtrace;
        unsigned int this_cpu;
+       unsigned long si_mask;
        unsigned long flags;
 
        if (per_cpu(watchdog_hardlockup_touched, cpu)) {
@@ -216,7 +217,8 @@ void watchdog_hardlockup_check(unsigned int cpu, struct 
pt_regs *regs)
                return;
        }
 
-       hardlockup_all_cpu_backtrace = (hardlockup_si_mask & SYS_INFO_ALL_BT) ?
+       si_mask = READ_ONCE(hardlockup_si_mask);
+       hardlockup_all_cpu_backtrace = (si_mask & SYS_INFO_ALL_BT) ?
                                        1 : sysctl_hardlockup_all_cpu_backtrace;
        /*
         * Check for a hardlockup by making sure the CPU's timer
@@ -286,7 +288,7 @@ void watchdog_hardlockup_check(unsigned int cpu, struct 
pt_regs *regs)
                        clear_bit_unlock(0, &hard_lockup_nmi_warn);
        }
 
-       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");
 
@@ -798,6 +800,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct 
hrtimer *hrtimer)
        struct pt_regs *regs = get_irq_regs();
        int softlockup_all_cpu_backtrace;
        int duration, thresh_count;
+       unsigned long si_mask;
        unsigned long flags;
 
        if (!watchdog_enabled)
@@ -809,7 +812,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct 
hrtimer *hrtimer)
        if (panic_in_progress())
                return HRTIMER_NORESTART;
 
-       softlockup_all_cpu_backtrace = (softlockup_si_mask & SYS_INFO_ALL_BT) ?
+       si_mask = READ_ONCE(softlockup_si_mask);
+       softlockup_all_cpu_backtrace = (si_mask & SYS_INFO_ALL_BT) ?
                                        1 : sysctl_softlockup_all_cpu_backtrace;
 
        watchdog_hardlockup_kick();
@@ -900,7 +904,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct 
hrtimer *hrtimer)
                }
 
                add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
-               sys_info(softlockup_si_mask & ~SYS_INFO_ALL_BT);
+               sys_info_with_filter(si_mask, SYS_INFO_ALL_BT);
                thresh_count = duration / get_softlockup_thresh();
 
                if (softlockup_panic && thresh_count >= softlockup_panic)
-- 
2.53.0