watchdog/hardlockup: Provide interface to stop/restart perf events

Provide an interface to stop and restart perf NMI watchdog events on all
CPUs. This is only usable during init and especially for handling the perf
HT bug on Intel machines. It's safe to use it this way as nothing can
start/stop the NMI watchdog in parallel.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Link: http://lkml.kernel.org/r/20170912194146.167649596@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index a36abe2da13e1a23edc8aa152205af143f658990..b24d4a58674aa2e33fca98bb53cecbf997095e0b 100644 (file)
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -75,7 +75,11 @@ static inline void hardlockup_detector_disable(void) {}
 
 #if defined(CONFIG_HARDLOCKUP_DETECTOR_PERF)
 extern void arch_touch_nmi_watchdog(void);
+extern void hardlockup_detector_perf_stop(void);
+extern void hardlockup_detector_perf_restart(void);
 #else
+static inline void hardlockup_detector_perf_stop(void) { }
+static inline void hardlockup_detector_perf_restart(void) { }
 #if !defined(CONFIG_HAVE_NMI_WATCHDOG)
 static inline void arch_touch_nmi_watchdog(void) {}
 #endif

diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 3a09ea1b1d3d5e6e284d058052403ac1396804ca..c9586ebc2e985a01c38a0125d78a240315b169eb 100644 (file)
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -261,3 +261,44 @@ void watchdog_nmi_disable(unsigned int cpu)
                        firstcpu_err = 0;
        }
 }
+
+/**
+ * hardlockup_detector_perf_stop - Globally stop watchdog events
+ *
+ * Special interface for x86 to handle the perf HT bug.
+ */
+void __init hardlockup_detector_perf_stop(void)
+{
+       int cpu;
+
+       lockdep_assert_cpus_held();
+
+       for_each_online_cpu(cpu) {
+               struct perf_event *event = per_cpu(watchdog_ev, cpu);
+
+               if (event)
+                       perf_event_disable(event);
+       }
+}
+
+/**
+ * hardlockup_detector_perf_restart - Globally restart watchdog events
+ *
+ * Special interface for x86 to handle the perf HT bug.
+ */
+void __init hardlockup_detector_perf_restart(void)
+{
+       int cpu;
+
+       lockdep_assert_cpus_held();
+
+       if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
+               return;
+
+       for_each_online_cpu(cpu) {
+               struct perf_event *event = per_cpu(watchdog_ev, cpu);
+
+               if (event)
+                       perf_event_enable(event);
+       }
+}