Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge tag 'sched-urgent-2020-07-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into master
Pull scheduler fixes from Ingo Molnar:
"Fix a race introduced by the recent loadavg race fix, plus add a debug
check for a hard to debug case of bogus wakeup function flags"
* tag 'sched-urgent-2020-07-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched: Warn if garbage is passed to default_wake_function()
sched: Fix race against ptrace_freeze_trace()
+15
-10
+15
-10
kernel/sched/core.c
+15
-10
kernel/sched/core.c
···
4119
4119
local_irq_disable();
4120
4120
rcu_note_context_switch(preempt);
4121
4121
4122
-
/* See deactivate_task() below. */
4123
-
prev_state = prev->state;
4124
-
4125
4122
/*
4126
4123
* Make sure that signal_pending_state()->signal_pending() below
4127
4124
* can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
···
4142
4145
update_rq_clock(rq);
4143
4146
4144
4147
switch_count = &prev->nivcsw;
4148
+
4145
4149
/*
4146
-
* We must re-load prev->state in case ttwu_remote() changed it
4147
-
* before we acquired rq->lock.
4150
+
* We must load prev->state once (task_struct::state is volatile), such
4151
+
* that:
4152
+
*
4153
+
* - we form a control dependency vs deactivate_task() below.
4154
+
* - ptrace_{,un}freeze_traced() can change ->state underneath us.
4148
4155
*/
4149
-
if (!preempt && prev_state && prev_state == prev->state) {
4156
+
prev_state = prev->state;
4157
+
if (!preempt && prev_state) {
4150
4158
if (signal_pending_state(prev_state, prev)) {
4151
4159
prev->state = TASK_RUNNING;
4152
4160
} else {
···
4165
4163
4166
4164
/*
4167
4165
* __schedule() ttwu()
4168
-
* prev_state = prev->state; if (READ_ONCE(p->on_rq) && ...)
4169
-
* LOCK rq->lock goto out;
4170
-
* smp_mb__after_spinlock(); smp_acquire__after_ctrl_dep();
4171
-
* p->on_rq = 0; p->state = TASK_WAKING;
4166
+
* prev_state = prev->state; if (p->on_rq && ...)
4167
+
* if (prev_state) goto out;
4168
+
* p->on_rq = 0; smp_acquire__after_ctrl_dep();
4169
+
* p->state = TASK_WAKING
4170
+
*
4171
+
* Where __schedule() and ttwu() have matching control dependencies.
4172
4172
*
4173
4173
* After this, schedule() must not care about p->state any more.
4174
4174
*/
···
4485
4481
int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
4486
4482
void *key)
4487
4483
{
4484
+
WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~WF_SYNC);
4488
4485
return try_to_wake_up(curr->private, mode, wake_flags);
4489
4486
}
4490
4487
EXPORT_SYMBOL(default_wake_function);