diff options
| author | Jiaxun Yang <[email protected]> | 2024-06-12 09:54:31 +0100 |
|---|---|---|
| committer | Thomas Bogendoerfer <[email protected]> | 2024-07-03 16:49:11 +0200 |
| commit | 7464c0762e96904b6bf686a4dc8b3255adf1c890 (patch) | |
| tree | 693d58354ef2ba4c7079d17987e22931c35fe540 | |
| parent | 426fa8e4fe7bb914b5977cbce453a9926bf5b2e6 (diff) | |
MIPS: csrc-r4k: Don't register as sched_clock if unfit
When we have more than one CPU in system, counter synchronisation
overhead can lead to a scenario that sched_clock goes backward when
being read from different CPUs.
This is accommodated by CONFIG_HAVE_UNSTABLE_SCHED_CLOCK, but it's
unavailable on 32bit kernel.
We don't want to risk sched_clock correctness, so if we have multiple
CPU in system and CONFIG_HAVE_UNSTABLE_SCHED_CLOCK is not set, we just
don't use counter as sched_clock source.
Signed-off-by: Jiaxun Yang <[email protected]>
Signed-off-by: Thomas Bogendoerfer <[email protected]>
| -rw-r--r-- | arch/mips/kernel/csrc-r4k.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c index 055747a7417d..bdb1fa8931f4 100644 --- a/arch/mips/kernel/csrc-r4k.c +++ b/arch/mips/kernel/csrc-r4k.c @@ -68,6 +68,18 @@ static bool rdhwr_count_usable(void) return false; } +static inline __init bool count_can_be_sched_clock(void) +{ + if (IS_ENABLED(CONFIG_CPU_FREQ)) + return false; + + if (num_possible_cpus() > 1 && + !IS_ENABLED(CONFIG_HAVE_UNSTABLE_SCHED_CLOCK)) + return false; + + return true; +} + #ifdef CONFIG_CPU_FREQ static bool __read_mostly r4k_clock_unstable; @@ -125,9 +137,8 @@ int __init init_r4k_clocksource(void) clocksource_register_hz(&clocksource_mips, mips_hpt_frequency); -#ifndef CONFIG_CPU_FREQ - sched_clock_register(r4k_read_sched_clock, 32, mips_hpt_frequency); -#endif + if (count_can_be_sched_clock()) + sched_clock_register(r4k_read_sched_clock, 32, mips_hpt_frequency); return 0; } |