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author | 2017-03-01 15:53:38 +0100 | |
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committer | 2017-03-02 08:50:49 +0100 | |
commit | f94c8d116997597fc00f0812b0ab9256e7b0c58f (patch) | |
tree | 9f2ea53d8def1a466727bcd9768e220ea7fb1164 /arch/x86 | |
parent | sched/core: Fix pick_next_task() for RT,DL (diff) | |
download | linux-f94c8d116997597fc00f0812b0ab9256e7b0c58f.tar.gz linux-f94c8d116997597fc00f0812b0ab9256e7b0c58f.tar.bz2 linux-f94c8d116997597fc00f0812b0ab9256e7b0c58f.zip |
sched/clock, x86/tsc: Rework the x86 'unstable' sched_clock() interface
Wanpeng Li reported that since the following commit:
acb04058de49 ("sched/clock: Fix hotplug crash")
... KVM always runs with unstable sched-clock even though KVM's
kvm_clock _is_ stable.
The problem is that we've tied clear_sched_clock_stable() to the TSC
state, and overlooked that sched_clock() is a paravirt function.
Solve this by doing two things:
- tie the sched_clock() stable state more clearly to the TSC stable
state for the normal (!paravirt) case.
- only call clear_sched_clock_stable() when we mark TSC unstable
when we use native_sched_clock().
The first means we can actually run with stable sched_clock in more
situations then before, which is good. And since commit:
12907fbb1a69 ("sched/clock, clocksource: Add optional cs::mark_unstable() method")
... this should be reliable. Since any detection of TSC fail now results
in marking the TSC unstable.
Reported-by: Wanpeng Li <kernellwp@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: acb04058de49 ("sched/clock: Fix hotplug crash")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/kernel/cpu/amd.c | 4 | ||||
-rw-r--r-- | arch/x86/kernel/cpu/centaur.c | 2 | ||||
-rw-r--r-- | arch/x86/kernel/cpu/common.c | 3 | ||||
-rw-r--r-- | arch/x86/kernel/cpu/cyrix.c | 1 | ||||
-rw-r--r-- | arch/x86/kernel/cpu/intel.c | 4 | ||||
-rw-r--r-- | arch/x86/kernel/cpu/transmeta.c | 2 | ||||
-rw-r--r-- | arch/x86/kernel/tsc.c | 35 |
7 files changed, 23 insertions, 28 deletions
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 4e95b2e0d95f..30d924ae5c34 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -555,10 +555,6 @@ static void early_init_amd(struct cpuinfo_x86 *c) if (c->x86_power & (1 << 8)) { set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC); - if (check_tsc_unstable()) - clear_sched_clock_stable(); - } else { - clear_sched_clock_stable(); } /* Bit 12 of 8000_0007 edx is accumulated power mechanism. */ diff --git a/arch/x86/kernel/cpu/centaur.c b/arch/x86/kernel/cpu/centaur.c index 2c234a6d94c4..bad8ff078a21 100644 --- a/arch/x86/kernel/cpu/centaur.c +++ b/arch/x86/kernel/cpu/centaur.c @@ -104,8 +104,6 @@ static void early_init_centaur(struct cpuinfo_x86 *c) #ifdef CONFIG_X86_64 set_cpu_cap(c, X86_FEATURE_SYSENTER32); #endif - - clear_sched_clock_stable(); } static void init_centaur(struct cpuinfo_x86 *c) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index c64ca5929cb5..9d98e2e15d54 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -86,7 +86,6 @@ static void default_init(struct cpuinfo_x86 *c) strcpy(c->x86_model_id, "386"); } #endif - clear_sched_clock_stable(); } static const struct cpu_dev default_cpu = { @@ -1075,8 +1074,6 @@ static void identify_cpu(struct cpuinfo_x86 *c) */ if (this_cpu->c_init) this_cpu->c_init(c); - else - clear_sched_clock_stable(); /* Disable the PN if appropriate */ squash_the_stupid_serial_number(c); diff --git a/arch/x86/kernel/cpu/cyrix.c b/arch/x86/kernel/cpu/cyrix.c index 47416f959a48..31e679238e8d 100644 --- a/arch/x86/kernel/cpu/cyrix.c +++ b/arch/x86/kernel/cpu/cyrix.c @@ -184,7 +184,6 @@ static void early_init_cyrix(struct cpuinfo_x86 *c) set_cpu_cap(c, X86_FEATURE_CYRIX_ARR); break; } - clear_sched_clock_stable(); } static void init_cyrix(struct cpuinfo_x86 *c) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 017ecd3bb553..2388bafe5c37 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -161,10 +161,6 @@ static void early_init_intel(struct cpuinfo_x86 *c) if (c->x86_power & (1 << 8)) { set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC); - if (check_tsc_unstable()) - clear_sched_clock_stable(); - } else { - clear_sched_clock_stable(); } /* Penwell and Cloverview have the TSC which doesn't sleep on S3 */ diff --git a/arch/x86/kernel/cpu/transmeta.c b/arch/x86/kernel/cpu/transmeta.c index c1ea5b999839..6a9ad73a2c54 100644 --- a/arch/x86/kernel/cpu/transmeta.c +++ b/arch/x86/kernel/cpu/transmeta.c @@ -15,8 +15,6 @@ static void early_init_transmeta(struct cpuinfo_x86 *c) if (xlvl >= 0x80860001) c->x86_capability[CPUID_8086_0001_EDX] = cpuid_edx(0x80860001); } - - clear_sched_clock_stable(); } static void init_transmeta(struct cpuinfo_x86 *c) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 2724dc82f992..911129fda2f9 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -326,9 +326,16 @@ unsigned long long sched_clock(void) { return paravirt_sched_clock(); } + +static inline bool using_native_sched_clock(void) +{ + return pv_time_ops.sched_clock == native_sched_clock; +} #else unsigned long long sched_clock(void) __attribute__((alias("native_sched_clock"))); + +static inline bool using_native_sched_clock(void) { return true; } #endif int check_tsc_unstable(void) @@ -1111,8 +1118,10 @@ static void tsc_cs_mark_unstable(struct clocksource *cs) { if (tsc_unstable) return; + tsc_unstable = 1; - clear_sched_clock_stable(); + if (using_native_sched_clock()) + clear_sched_clock_stable(); disable_sched_clock_irqtime(); pr_info("Marking TSC unstable due to clocksource watchdog\n"); } @@ -1134,18 +1143,20 @@ static struct clocksource clocksource_tsc = { void mark_tsc_unstable(char *reason) { - if (!tsc_unstable) { - tsc_unstable = 1; + if (tsc_unstable) + return; + + tsc_unstable = 1; + if (using_native_sched_clock()) clear_sched_clock_stable(); - disable_sched_clock_irqtime(); - pr_info("Marking TSC unstable due to %s\n", reason); - /* Change only the rating, when not registered */ - if (clocksource_tsc.mult) - clocksource_mark_unstable(&clocksource_tsc); - else { - clocksource_tsc.flags |= CLOCK_SOURCE_UNSTABLE; - clocksource_tsc.rating = 0; - } + disable_sched_clock_irqtime(); + pr_info("Marking TSC unstable due to %s\n", reason); + /* Change only the rating, when not registered */ + if (clocksource_tsc.mult) { + clocksource_mark_unstable(&clocksource_tsc); + } else { + clocksource_tsc.flags |= CLOCK_SOURCE_UNSTABLE; + clocksource_tsc.rating = 0; } } |