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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 /kernel | |
parent | 54ecb8f7028c5eb3d740bb82b0f1d90f2df63c5c (diff) | |
download | linux-01b4c39901e087ceebae2733857248de81476bd8.tar.bz2 |
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 'kernel')
-rw-r--r-- | kernel/time/tick-sched.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 955851748dc3..d1b0a84b6112 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -198,6 +198,11 @@ static bool check_tick_dependency(atomic_t *dep) return true; } + if (val & TICK_DEP_MASK_RCU) { + trace_tick_stop(0, TICK_DEP_MASK_RCU); + return true; + } + return false; } @@ -324,6 +329,7 @@ void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) preempt_enable(); } } +EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu); void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { @@ -331,6 +337,7 @@ void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) atomic_andnot(BIT(bit), &ts->tick_dep_mask); } +EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu); /* * Set a per-task tick dependency. Posix CPU timers need this in order to elapse |