forked from mirrors/linux
ipc/sem.c: move wake_up_process out of the spinlock section
The wake-up part of semtimedop() consists out of two steps: - the right tasks must be identified. - they must be woken up. Right now, both steps run while the array spinlock is held. This patch reorders the code and moves the actual wake_up_process() behind the point where the spinlock is dropped. The code also moves setting sem->sem_otime to one place: It does not make sense to set the last modify time multiple times. [akpm@linux-foundation.org: repair kerneldoc] [akpm@linux-foundation.org: fix uninitialised retval] Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Cc: Chris Mason <chris.mason@oracle.com> Cc: Zach Brown <zach.brown@oracle.com> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Nick Piggin <npiggin@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Manfred Spraul
Linus Torvalds
parent
fd5db42254
commit
0a2b9d4c79
1 changed files with 91 additions and 32 deletions
109
ipc/sem.c
109
ipc/sem.c
|
|
@ -381,7 +381,6 @@ static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
|
|||
sop--;
|
||||
}
|
||||
|
||||
sma->sem_otime = get_seconds();
|
||||
return 0;
|
||||
|
||||
out_of_range:
|
||||
|
|
@ -404,24 +403,50 @@ static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
|
|||
return result;
|
||||
}
|
||||
|
||||
/*
|
||||
* Wake up a process waiting on the sem queue with a given error.
|
||||
* The queue is invalid (may not be accessed) after the function returns.
|
||||
/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
|
||||
* @q: queue entry that must be signaled
|
||||
* @error: Error value for the signal
|
||||
*
|
||||
* Prepare the wake-up of the queue entry q.
|
||||
*/
|
||||
static void wake_up_sem_queue(struct sem_queue *q, int error)
|
||||
static void wake_up_sem_queue_prepare(struct list_head *pt,
|
||||
struct sem_queue *q, int error)
|
||||
{
|
||||
if (list_empty(pt)) {
|
||||
/*
|
||||
* Hold preempt off so that we don't get preempted and have the
|
||||
* wakee busy-wait until we're scheduled back on. We're holding
|
||||
* locks here so it may not strictly be needed, however if the
|
||||
* locks become preemptible then this prevents such a problem.
|
||||
* wakee busy-wait until we're scheduled back on.
|
||||
*/
|
||||
preempt_disable();
|
||||
}
|
||||
q->status = IN_WAKEUP;
|
||||
q->pid = error;
|
||||
|
||||
list_add_tail(&q->simple_list, pt);
|
||||
}
|
||||
|
||||
/**
|
||||
* wake_up_sem_queue_do(pt) - do the actual wake-up
|
||||
* @pt: list of tasks to be woken up
|
||||
*
|
||||
* Do the actual wake-up.
|
||||
* The function is called without any locks held, thus the semaphore array
|
||||
* could be destroyed already and the tasks can disappear as soon as the
|
||||
* status is set to the actual return code.
|
||||
*/
|
||||
static void wake_up_sem_queue_do(struct list_head *pt)
|
||||
{
|
||||
struct sem_queue *q, *t;
|
||||
int did_something;
|
||||
|
||||
did_something = !list_empty(pt);
|
||||
list_for_each_entry_safe(q, t, pt, simple_list) {
|
||||
wake_up_process(q->sleeper);
|
||||
/* hands-off: q can disappear immediately after writing q->status. */
|
||||
/* q can disappear immediately after writing q->status. */
|
||||
smp_wmb();
|
||||
q->status = error;
|
||||
q->status = q->pid;
|
||||
}
|
||||
if (did_something)
|
||||
preempt_enable();
|
||||
}
|
||||
|
||||
|
|
@ -502,17 +527,22 @@ static int check_restart(struct sem_array *sma, struct sem_queue *q)
|
|||
* update_queue(sma, semnum): Look for tasks that can be completed.
|
||||
* @sma: semaphore array.
|
||||
* @semnum: semaphore that was modified.
|
||||
* @pt: list head for the tasks that must be woken up.
|
||||
*
|
||||
* update_queue must be called after a semaphore in a semaphore array
|
||||
* was modified. If multiple semaphore were modified, then @semnum
|
||||
* must be set to -1.
|
||||
* The tasks that must be woken up are added to @pt. The return code
|
||||
* is stored in q->pid.
|
||||
* The function return 1 if at least one semop was completed successfully.
|
||||
*/
|
||||
static void update_queue(struct sem_array *sma, int semnum)
|
||||
static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
|
||||
{
|
||||
struct sem_queue *q;
|
||||
struct list_head *walk;
|
||||
struct list_head *pending_list;
|
||||
int offset;
|
||||
int semop_completed = 0;
|
||||
|
||||
/* if there are complex operations around, then knowing the semaphore
|
||||
* that was modified doesn't help us. Assume that multiple semaphores
|
||||
|
|
@ -557,40 +587,55 @@ static void update_queue(struct sem_array *sma, int semnum)
|
|||
|
||||
unlink_queue(sma, q);
|
||||
|
||||
if (error)
|
||||
if (error) {
|
||||
restart = 0;
|
||||
else
|
||||
} else {
|
||||
semop_completed = 1;
|
||||
restart = check_restart(sma, q);
|
||||
}
|
||||
|
||||
wake_up_sem_queue(q, error);
|
||||
wake_up_sem_queue_prepare(pt, q, error);
|
||||
if (restart)
|
||||
goto again;
|
||||
}
|
||||
return semop_completed;
|
||||
}
|
||||
|
||||
/** do_smart_update(sma, sops, nsops): Optimized update_queue
|
||||
/**
|
||||
* do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
|
||||
* @sma: semaphore array
|
||||
* @sops: operations that were performed
|
||||
* @nsops: number of operations
|
||||
* @otime: force setting otime
|
||||
* @pt: list head of the tasks that must be woken up.
|
||||
*
|
||||
* do_smart_update() does the required called to update_queue, based on the
|
||||
* actual changes that were performed on the semaphore array.
|
||||
* Note that the function does not do the actual wake-up: the caller is
|
||||
* responsible for calling wake_up_sem_queue_do(@pt).
|
||||
* It is safe to perform this call after dropping all locks.
|
||||
*/
|
||||
static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops)
|
||||
static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
|
||||
int otime, struct list_head *pt)
|
||||
{
|
||||
int i;
|
||||
|
||||
if (sma->complex_count || sops == NULL) {
|
||||
update_queue(sma, -1);
|
||||
return;
|
||||
if (update_queue(sma, -1, pt))
|
||||
otime = 1;
|
||||
goto done;
|
||||
}
|
||||
|
||||
for (i = 0; i < nsops; i++) {
|
||||
if (sops[i].sem_op > 0 ||
|
||||
(sops[i].sem_op < 0 &&
|
||||
sma->sem_base[sops[i].sem_num].semval == 0))
|
||||
update_queue(sma, sops[i].sem_num);
|
||||
if (update_queue(sma, sops[i].sem_num, pt))
|
||||
otime = 1;
|
||||
}
|
||||
done:
|
||||
if (otime)
|
||||
sma->sem_otime = get_seconds();
|
||||
}
|
||||
|
||||
|
||||
|
|
@ -656,6 +701,7 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
|
|||
struct sem_undo *un, *tu;
|
||||
struct sem_queue *q, *tq;
|
||||
struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
|
||||
struct list_head tasks;
|
||||
|
||||
/* Free the existing undo structures for this semaphore set. */
|
||||
assert_spin_locked(&sma->sem_perm.lock);
|
||||
|
|
@ -669,15 +715,17 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
|
|||
}
|
||||
|
||||
/* Wake up all pending processes and let them fail with EIDRM. */
|
||||
INIT_LIST_HEAD(&tasks);
|
||||
list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
|
||||
unlink_queue(sma, q);
|
||||
wake_up_sem_queue(q, -EIDRM);
|
||||
wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
|
||||
}
|
||||
|
||||
/* Remove the semaphore set from the IDR */
|
||||
sem_rmid(ns, sma);
|
||||
sem_unlock(sma);
|
||||
|
||||
wake_up_sem_queue_do(&tasks);
|
||||
ns->used_sems -= sma->sem_nsems;
|
||||
security_sem_free(sma);
|
||||
ipc_rcu_putref(sma);
|
||||
|
|
@ -799,11 +847,13 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
|
|||
ushort fast_sem_io[SEMMSL_FAST];
|
||||
ushort* sem_io = fast_sem_io;
|
||||
int nsems;
|
||||
struct list_head tasks;
|
||||
|
||||
sma = sem_lock_check(ns, semid);
|
||||
if (IS_ERR(sma))
|
||||
return PTR_ERR(sma);
|
||||
|
||||
INIT_LIST_HEAD(&tasks);
|
||||
nsems = sma->sem_nsems;
|
||||
|
||||
err = -EACCES;
|
||||
|
|
@ -891,7 +941,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
|
|||
}
|
||||
sma->sem_ctime = get_seconds();
|
||||
/* maybe some queued-up processes were waiting for this */
|
||||
update_queue(sma, -1);
|
||||
do_smart_update(sma, NULL, 0, 0, &tasks);
|
||||
err = 0;
|
||||
goto out_unlock;
|
||||
}
|
||||
|
|
@ -933,13 +983,15 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
|
|||
curr->sempid = task_tgid_vnr(current);
|
||||
sma->sem_ctime = get_seconds();
|
||||
/* maybe some queued-up processes were waiting for this */
|
||||
update_queue(sma, semnum);
|
||||
do_smart_update(sma, NULL, 0, 0, &tasks);
|
||||
err = 0;
|
||||
goto out_unlock;
|
||||
}
|
||||
}
|
||||
out_unlock:
|
||||
sem_unlock(sma);
|
||||
wake_up_sem_queue_do(&tasks);
|
||||
|
||||
out_free:
|
||||
if(sem_io != fast_sem_io)
|
||||
ipc_free(sem_io, sizeof(ushort)*nsems);
|
||||
|
|
@ -1213,6 +1265,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
|
|||
struct sem_queue queue;
|
||||
unsigned long jiffies_left = 0;
|
||||
struct ipc_namespace *ns;
|
||||
struct list_head tasks;
|
||||
|
||||
ns = current->nsproxy->ipc_ns;
|
||||
|
||||
|
|
@ -1261,6 +1314,8 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
|
|||
} else
|
||||
un = NULL;
|
||||
|
||||
INIT_LIST_HEAD(&tasks);
|
||||
|
||||
sma = sem_lock_check(ns, semid);
|
||||
if (IS_ERR(sma)) {
|
||||
if (un)
|
||||
|
|
@ -1309,7 +1364,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
|
|||
error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
|
||||
if (error <= 0) {
|
||||
if (alter && error == 0)
|
||||
do_smart_update(sma, sops, nsops);
|
||||
do_smart_update(sma, sops, nsops, 1, &tasks);
|
||||
|
||||
goto out_unlock_free;
|
||||
}
|
||||
|
|
@ -1386,6 +1441,8 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
|
|||
|
||||
out_unlock_free:
|
||||
sem_unlock(sma);
|
||||
|
||||
wake_up_sem_queue_do(&tasks);
|
||||
out_free:
|
||||
if(sops != fast_sops)
|
||||
kfree(sops);
|
||||
|
|
@ -1446,6 +1503,7 @@ void exit_sem(struct task_struct *tsk)
|
|||
for (;;) {
|
||||
struct sem_array *sma;
|
||||
struct sem_undo *un;
|
||||
struct list_head tasks;
|
||||
int semid;
|
||||
int i;
|
||||
|
||||
|
|
@ -1509,10 +1567,11 @@ void exit_sem(struct task_struct *tsk)
|
|||
semaphore->sempid = task_tgid_vnr(current);
|
||||
}
|
||||
}
|
||||
sma->sem_otime = get_seconds();
|
||||
/* maybe some queued-up processes were waiting for this */
|
||||
update_queue(sma, -1);
|
||||
INIT_LIST_HEAD(&tasks);
|
||||
do_smart_update(sma, NULL, 0, 1, &tasks);
|
||||
sem_unlock(sma);
|
||||
wake_up_sem_queue_do(&tasks);
|
||||
|
||||
call_rcu(&un->rcu, free_un);
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in a new issue