From: Qais Yousef qais.yousef@arm.com
[ Upstream commit e65855a52b479f98674998cb23b21ef5a8144b04 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index db1e99756c400..f788cd61df212 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1248,6 +1248,15 @@ 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; }
@@ -1278,8 +1287,6 @@ 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);