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mtx: remove the stupid

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This commit is contained in:
anna 2021-10-16 04:23:05 +02:00
parent ad422894f2
commit 721ba69276
Signed by: fef
GPG key ID: EC22E476DC2D3D84
2 changed files with 27 additions and 24 deletions
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2
include/gay/mutex.h
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@ -21,8 +21,8 @@ int spin_trylock(spin_t *spin);
void spin_unlock(spin_t *spin); void spin_unlock(spin_t *spin);
struct lock_waiter { struct lock_waiter {
struct task *task;
struct clist clink; struct clist clink;
struct task *task;
}; };
struct mtx { struct mtx {

49
kernel/mutex.c
View file

@ -40,32 +40,35 @@ void mtx_init(struct mtx *mtx)
void mtx_lock(struct mtx *mtx) void mtx_lock(struct mtx *mtx)
{ {
while (1) { /*
* acquire a lock on the wait queue before trying to claim the
* mutex itself to make sure the mutex isn't released while we
* are inserting ourselves into the wait queue
*/
spin_lock(&mtx->wait_queue_lock);
if (atom_write(&mtx->lock, 1) == 0) {
spin_unlock(&mtx->wait_queue_lock);
} else {
struct task *task = current;
/* /*
* acquire a lock on the wait queue before trying to claim the * It might not be the smartest idea to allocate this thing on
* mutex itself to make sure the mutex isn't released while we * the stack because it's gonna blow up if the task somehow dies
* are inserting ourselves into the wait queue * before returning here. Let's see how this turns out.
*/ */
spin_lock(&mtx->wait_queue_lock); struct lock_waiter waiter = {
if (atom_write(&mtx->lock, 1) == 0) { .task = task,
spin_unlock(&mtx->wait_queue_lock); };
break; clist_add(&mtx->wait_queue, &waiter.clink);
} else { spin_unlock(&mtx->wait_queue_lock);
struct task *cur = current;
/*
* It might not be the smartest idea to allocate this thing on
* the stack because it's gonna blow up if the task somehow dies
* before returning here. Let's see how this turns out.
*/
struct lock_waiter waiter = {
.task = cur,
};
clist_add(&mtx->wait_queue, &waiter.clink);
spin_unlock(&mtx->wait_queue_lock);
cur->state = TASK_BLOCKED; task->state = TASK_BLOCKED;
schedule(); /*
} * This is only gonna return when the task currently owning the
* lock releases it. In that case, it doesn't unlock the mutex
* but merely switches back to us directly and thereby implicitly
* transfers the ownership of the mutex to us (see mtx_unlock()).
*/
schedule();
} }
} }