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ipc/sem.c: remove code duplication

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count_semzcnt and count_semncnt are more of less identical.  The patch
creates a single function that either counts the number of tasks waiting
for zero or waiting due to a decrease operation.

Compared to the initial version, the BUG_ONs were removed.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
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 2014-06-06 14:37:48 -07:00 committed by Linus Torvalds
parent 1994862dc9
commit 2f2ed41dca
1 changed files with 51 additions and 56 deletions
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107
ipc/sem.c
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@ -47,8 +47,7 @@
* Thus: Perfect SMP scaling between independent semaphore arrays.
* If multiple semaphores in one array are used, then cache line
* trashing on the semaphore array spinlock will limit the scaling.
* - semncnt and semzcnt are calculated on demand in count_semncnt() and
* count_semzcnt()
* - semncnt and semzcnt are calculated on demand in count_semcnt()
* - the task that performs a successful semop() scans the list of all
* sleeping tasks and completes any pending operations that can be fulfilled.
* Semaphores are actively given to waiting tasks (necessary for FIFO).
@ -989,6 +988,31 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop
set_semotime(sma, sops);
}
/*
* check_qop: Test how often a queued operation sleeps on the semaphore semnum
*/
static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
bool count_zero)
{
struct sembuf *sops = q->sops;
int nsops = q->nsops;
int i, semcnt;
semcnt = 0;
for (i = 0; i < nsops; i++) {
if (sops[i].sem_num != semnum)
continue;
if (sops[i].sem_flg & IPC_NOWAIT)
continue;
if (count_zero && sops[i].sem_op == 0)
semcnt++;
if (!count_zero && sops[i].sem_op < 0)
semcnt++;
}
return semcnt;
}
/* The following counts are associated to each semaphore:
* semncnt number of tasks waiting on semval being nonzero
* semzcnt number of tasks waiting on semval being zero
@ -998,66 +1022,37 @@ static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsop
* The counts we return here are a rough approximation, but still
* warrant that semncnt+semzcnt>0 if the task is on the pending queue.
*/
static int count_semncnt(struct sem_array *sma, ushort semnum)
static int count_semcnt(struct sem_array *sma, ushort semnum,
bool count_zero)
{
int semncnt;
struct list_head *l;
struct sem_queue *q;
int semcnt;
semncnt = 0;
list_for_each_entry(q, &sma->sem_base[semnum].pending_alter, list) {
struct sembuf *sops = q->sops;
BUG_ON(sops->sem_num != semnum);
if ((sops->sem_op < 0) && !(sops->sem_flg & IPC_NOWAIT))
semncnt++;
semcnt = 0;
/* First: check the simple operations. They are easy to evaluate */
if (count_zero)
l = &sma->sem_base[semnum].pending_const;
else
l = &sma->sem_base[semnum].pending_alter;
list_for_each_entry(q, l, list) {
/* all task on a per-semaphore list sleep on exactly
* that semaphore
*/
semcnt++;
}
/* Then: check the complex operations. */
list_for_each_entry(q, &sma->pending_alter, list) {
struct sembuf *sops = q->sops;
int nsops = q->nsops;
int i;
for (i = 0; i < nsops; i++)
if (sops[i].sem_num == semnum
&& (sops[i].sem_op < 0)
&& !(sops[i].sem_flg & IPC_NOWAIT))
semncnt++;
semcnt += check_qop(sma, semnum, q, count_zero);
}
return semncnt;
}
static int count_semzcnt(struct sem_array *sma, ushort semnum)
{
int semzcnt;
struct sem_queue *q;
semzcnt = 0;
list_for_each_entry(q, &sma->sem_base[semnum].pending_const, list) {
struct sembuf *sops = q->sops;
BUG_ON(sops->sem_num != semnum);
if ((sops->sem_op == 0) && !(sops->sem_flg & IPC_NOWAIT))
semzcnt++;
if (count_zero) {
list_for_each_entry(q, &sma->pending_const, list) {
semcnt += check_qop(sma, semnum, q, count_zero);
}
}
list_for_each_entry(q, &sma->pending_const, list) {
struct sembuf *sops = q->sops;
int nsops = q->nsops;
int i;
for (i = 0; i < nsops; i++)
if (sops[i].sem_num == semnum
&& (sops[i].sem_op == 0)
&& !(sops[i].sem_flg & IPC_NOWAIT))
semzcnt++;
}
list_for_each_entry(q, &sma->pending_alter, list) {
struct sembuf *sops = q->sops;
int nsops = q->nsops;
int i;
for (i = 0; i < nsops; i++)
if (sops[i].sem_num == semnum
&& (sops[i].sem_op == 0)
&& !(sops[i].sem_flg & IPC_NOWAIT))
semzcnt++;
}
return semzcnt;
return semcnt;
}
/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
@ -1459,10 +1454,10 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
err = curr->sempid;
goto out_unlock;
case GETNCNT:
err = count_semncnt(sma, semnum);
err = count_semcnt(sma, semnum, 0);
goto out_unlock;
case GETZCNT:
err = count_semzcnt(sma, semnum);
err = count_semcnt(sma, semnum, 1);
goto out_unlock;
}