diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2017-03-01 15:53:38 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-03-02 08:50:49 +0100 |
| commit | f94c8d116997597fc00f0812b0ab9256e7b0c58f (patch) | |
| tree | 9f2ea53d8def1a466727bcd9768e220ea7fb1164 /arch/x86/kernel/cpu/common.c | |
| parent | 0ba87bb27d66b78e278167ac7e20c66520b8a612 (diff) | |
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/kernel/cpu/common.c')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 3 |
1 files changed, 0 insertions, 3 deletions
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); |