diff options
| author | Frederic Weisbecker <frederic@kernel.org> | 2019-07-24 15:22:59 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2019-10-05 10:45:16 -0700 |
| commit | 01b4c39901e087ceebae2733857248de81476bd8 (patch) | |
| tree | 72bdea923f0fc822c57b1cc916c596d2bf6682b3 /include/linux/tick.h | |
| parent | 54ecb8f7028c5eb3d740bb82b0f1d90f2df63c5c (diff) | |
nohz: Add TICK_DEP_BIT_RCU
If a nohz_full CPU is looping in the kernel, the scheduling-clock tick
might nevertheless remain disabled. In !PREEMPT kernels, this can
prevent RCU's attempts to enlist the aid of that CPU's executions of
cond_resched(), which can in turn result in an arbitrarily delayed grace
period and thus an OOM. RCU therefore needs a way to enable a holdout
nohz_full CPU's scheduler-clock interrupt.
This commit therefore provides a new TICK_DEP_BIT_RCU value which RCU can
pass to tick_dep_set_cpu() and friends to force on the scheduler-clock
interrupt for a specified CPU or task. In some cases, rcutorture needs
to turn on the scheduler-clock tick, so this commit also exports the
relevant symbols to GPL-licensed modules.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'include/linux/tick.h')
| -rw-r--r-- | include/linux/tick.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/include/linux/tick.h b/include/linux/tick.h index f92a10b5e112..39eb44564058 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -108,7 +108,8 @@ enum tick_dep_bits { TICK_DEP_BIT_POSIX_TIMER = 0, TICK_DEP_BIT_PERF_EVENTS = 1, TICK_DEP_BIT_SCHED = 2, - TICK_DEP_BIT_CLOCK_UNSTABLE = 3 + TICK_DEP_BIT_CLOCK_UNSTABLE = 3, + TICK_DEP_BIT_RCU = 4 }; #define TICK_DEP_MASK_NONE 0 @@ -116,6 +117,7 @@ enum tick_dep_bits { #define TICK_DEP_MASK_PERF_EVENTS (1 << TICK_DEP_BIT_PERF_EVENTS) #define TICK_DEP_MASK_SCHED (1 << TICK_DEP_BIT_SCHED) #define TICK_DEP_MASK_CLOCK_UNSTABLE (1 << TICK_DEP_BIT_CLOCK_UNSTABLE) +#define TICK_DEP_MASK_RCU (1 << TICK_DEP_BIT_RCU) #ifdef CONFIG_NO_HZ_COMMON extern bool tick_nohz_enabled; @@ -268,6 +270,9 @@ static inline bool tick_nohz_full_enabled(void) { return false; } static inline bool tick_nohz_full_cpu(int cpu) { return false; } static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { } +static inline void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) { } +static inline void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { } + static inline void tick_dep_set(enum tick_dep_bits bit) { } static inline void tick_dep_clear(enum tick_dep_bits bit) { } static inline void tick_dep_set_cpu(int cpu, enum tick_dep_bits bit) { } |