Commit-ID: 0f0b7e1cc7abf8e1a8b301f2868379d611d05ae2 Gitweb: https://git.kernel.org/tip/0f0b7e1cc7abf8e1a8b301f2868379d611d05ae2 Author: Juri Lelli <juri.le...@redhat.com> AuthorDate: Thu, 7 Mar 2019 13:09:13 +0100 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Fri, 22 Mar 2019 14:14:58 +0100
x86/tsc: Add option to disable tsc clocksource watchdog Clocksource watchdog has been found responsible for generating latency spikes (in the 10-20 us range) when woken up to check for TSC stability. Add an option to disable it at boot. Signed-off-by: Juri Lelli <juri.le...@redhat.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: bige...@linutronix.de Cc: linux-rt-us...@vger.kernel.org Cc: pet...@infradead.org Cc: bris...@redhat.com Cc: willi...@redhat.com Link: https://lkml.kernel.org/r/20190307120913.13168-1-juri.le...@redhat.com --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ arch/x86/kernel/tsc.c | 5 ++++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2b8ee90bb644..c4d830003b21 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4703,6 +4703,10 @@ [x86] unstable: mark the TSC clocksource as unstable, this marks the TSC unconditionally unstable at bootup and avoids any further wobbles once the TSC watchdog notices. + [x86] nowatchdog: disable clocksource watchdog. Used + in situations with strict latency requirements (where + interruptions from clocksource watchdog are not + acceptable). turbografx.map[2|3]= [HW,JOY] TurboGraFX parallel port interface diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 3fae23834069..aab0c82e0a0d 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -283,6 +283,7 @@ int __init notsc_setup(char *str) __setup("notsc", notsc_setup); static int no_sched_irq_time; +static int no_tsc_watchdog; static int __init tsc_setup(char *str) { @@ -292,6 +293,8 @@ static int __init tsc_setup(char *str) no_sched_irq_time = 1; if (!strcmp(str, "unstable")) mark_tsc_unstable("boot parameter"); + if (!strcmp(str, "nowatchdog")) + no_tsc_watchdog = 1; return 1; } @@ -1349,7 +1352,7 @@ static int __init init_tsc_clocksource(void) if (tsc_unstable) goto unreg; - if (tsc_clocksource_reliable) + if (tsc_clocksource_reliable || no_tsc_watchdog) clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY; if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3))
