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| author |   Qais Yousef <qais.yousef@arm.com> | 2020-07-16 12:03:47 +0100 |
|---|---|---|
| committer |   Peter Zijlstra <peterz@infradead.org> | 2020-07-29 13:51:47 +0200 |
| commit | e65855a52b479f98674998cb23b21ef5a8144b04 (patch) | |
| tree | ea641813091126bbc0d7ef4ec02b938cbe8488d8 /kernel/sched | |
| parent | sched: Remove duplicated tick_nohz_full_enabled() check (diff) | |
| download | wireguard-linux-e65855a52b479f98674998cb23b21ef5a8144b04.tar.xz wireguard-linux-e65855a52b479f98674998cb23b21ef5a8144b04.zip | |
sched/uclamp: Fix a deadlock when enabling uclamp static key
The following splat was caught when setting uclamp value of a task:
BUG: sleeping function called from invalid context at ./include/linux/percpu-rwsem.h:49
cpus_read_lock+0x68/0x130
static_key_enable+0x1c/0x38
__sched_setscheduler+0x900/0xad8
Fix by ensuring we enable the key outside of the critical section in
__sched_setscheduler()
Fixes: 46609ce22703 ("sched/uclamp: Protect uclamp fast path code with static key")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200716110347.19553-4-qais.yousef@arm.com
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 678253450ebb..e44d83f3e0e6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1346,6 +1346,15 @@ static int uclamp_validate(struct task_struct *p, if (upper_bound > SCHED_CAPACITY_SCALE) return -EINVAL; + /* + * We have valid uclamp attributes; make sure uclamp is enabled. + * + * We need to do that here, because enabling static branches is a + * blocking operation which obviously cannot be done while holding + * scheduler locks. + */ + static_branch_enable(&sched_uclamp_used); + return 0; } @@ -1376,8 +1385,6 @@ static void __setscheduler_uclamp(struct task_struct *p, if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP))) return; - static_branch_enable(&sched_uclamp_used); - if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) { uclamp_se_set(&p->uclamp_req[UCLAMP_MIN], attr->sched_util_min, true); |