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kernel: events: fix waitq timeout race condition

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Updates events to prevent a timeout from corrupting the list of
threads that needs to be waken up.

Signed-off-by: Aastha Grover <aastha.grover@intel.com>
This commit is contained in:
Aastha Grover 2023-03-08 16:56:31 -05:00 committed by Carles Cufí
parent 5537776898
commit 877fc3d508
4 changed files with 33 additions and 8 deletions
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3
include/zephyr/kernel/thread.h
View File

@ -264,6 +264,9 @@ struct k_thread {
uint32_t events;
uint32_t event_options;
/** true if timeout should not wake the thread */
bool no_wake_on_timeout;
#endif
#if defined(CONFIG_THREAD_MONITOR)

25
kernel/events.c
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@ -98,13 +98,22 @@ static int event_walk_op(struct k_thread *thread, void *data)
if (are_wait_conditions_met(thread->events, event_data->events,
wait_condition)) {
/*
* Events create a list of threads to wake up. We do
* not want z_thread_timeout to wake these threads; they
* will be woken up by k_event_post_internal once they
* have been processed.
*/
thread->no_wake_on_timeout = true;
/*
* The wait conditions have been satisfied. Add this
* thread to the list of threads to unpend.
*/
thread->next_event_link = event_data->head;
event_data->head = thread;
z_abort_timeout(&thread->base.timeout);
}
return 0;
@ -129,11 +138,10 @@ static void k_event_post_internal(struct k_event *event, uint32_t events,
data.events = events;
/*
* Posting an event has the potential to wake multiple pended threads.
* It is desirable to unpend all affected threads simultaneously. To
* do so, this must be done in three steps as it is unsafe to unpend
* threads from within the _WAIT_Q_FOR_EACH() loop.
* It is desirable to unpend all affected threads simultaneously. This
* is done in three steps:
*
* 1. Create a linked list of threads to unpend.
* 1. Walk the waitq and create a linked list of threads to unpend.
* 2. Unpend each of the threads in the linked list
* 3. Ready each of the threads in the linked list
*/
@ -142,12 +150,13 @@ static void k_event_post_internal(struct k_event *event, uint32_t events,
if (data.head != NULL) {
thread = data.head;
struct k_thread *next;
do {
z_unpend_thread(thread);
arch_thread_return_value_set(thread, 0);
thread->events = events;
z_ready_thread(thread);
thread = thread->next_event_link;
next = thread->next_event_link;
z_sched_wake_thread(thread, false);
thread = next;
} while (thread != NULL);
}

10
kernel/sched.c
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@ -805,6 +805,16 @@ void z_sched_wake_thread(struct k_thread *thread, bool is_timeout)
bool killed = ((thread->base.thread_state & _THREAD_DEAD) ||
(thread->base.thread_state & _THREAD_ABORTING));
#ifdef CONFIG_EVENTS
bool do_nothing = thread->no_wake_on_timeout && is_timeout;
thread->no_wake_on_timeout = false;
if (do_nothing) {
continue;
}
#endif
if (!killed) {
/* The thread is not being killed */
if (thread->base.pended_on != NULL) {

3
kernel/thread.c
View File

@ -578,6 +578,9 @@ char *z_setup_new_thread(struct k_thread *new_thread,
/* Initialize custom data field (value is opaque to kernel) */
new_thread->custom_data = NULL;
#endif
#ifdef CONFIG_EVENTS
new_thread->no_wake_on_timeout = false;
#endif
#ifdef CONFIG_THREAD_MONITOR
new_thread->entry.pEntry = entry;
new_thread->entry.parameter1 = p1;