Revert "perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86"

This reverts commit 2c95afc1e83d93fac3be6923465e1753c2c53b0a.

Stephane reported the following regression:

 > Since Andi added:
 >
 > commit 2c95afc1e83d93fac3be6923465e1753c2c53b0a
 > Author: Andi Kleen <[email protected]>
 > Date:   Thu Jun 9 06:14:38 2016 -0700
 >
 >    perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86
 >
 > $ perf stat -e ref-cycles ls
 >   <not counted> ....
 >
 > fails systematically because the ref-cycles is now used by the
 > watchdog and given this is a system-wide pinned event, it monopolizes
 > the fixed counter 2 which is the only counter able to measure this event.

Since the next merge window is near, fix the regression for now
by reverting the commit.

Reported-by: Stephane Eranian <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index 016f4263fad473962f61359ac641be41db7a808a..7788ce643bf4577d443b1007a1e4d37c8d28aaff 100644 (file)
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -18,16 +18,8 @@
 #include <linux/nmi.h>
 #include <linux/module.h>
 #include <linux/delay.h>
-#include <linux/perf_event.h>
 
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
-int hw_nmi_get_event(void)
-{
-       if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
-               return PERF_COUNT_HW_REF_CPU_CYCLES;
-       return PERF_COUNT_HW_CPU_CYCLES;
-}
-
 u64 hw_nmi_get_sample_period(int watchdog_thresh)
 {
        return (u64)(cpu_khz) * 1000 * watchdog_thresh;

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 79858af272090a881bef7fc66ddbd1330d03f0c2..4630eeae18e08df43be6567ca5fbcb2027643c65 100644 (file)
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -66,7 +66,6 @@ static inline bool trigger_allbutself_cpu_backtrace(void)
 
 #ifdef CONFIG_LOCKUP_DETECTOR
 u64 hw_nmi_get_sample_period(int watchdog_thresh);
-int hw_nmi_get_event(void);
 extern int nmi_watchdog_enabled;
 extern int soft_watchdog_enabled;
 extern int watchdog_user_enabled;

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 8dd30fcd91be967dcca8e3ddf7050dde23b37227..9acb29f280ec95813612a913307e4dcaec8b7e03 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -315,12 +315,6 @@ static int is_softlockup(unsigned long touch_ts)
 
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
 
-/* Can be overriden by architecture */
-__weak int hw_nmi_get_event(void)
-{
-       return PERF_COUNT_HW_CPU_CYCLES;
-}
-
 static struct perf_event_attr wd_hw_attr = {
        .type           = PERF_TYPE_HARDWARE,
        .config         = PERF_COUNT_HW_CPU_CYCLES,
@@ -610,7 +604,6 @@ static int watchdog_nmi_enable(unsigned int cpu)
 
        wd_attr = &wd_hw_attr;
        wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
-       wd_attr->config = hw_nmi_get_event();
 
        /* Try to register using hardware perf events */
        event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);