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Code Issues Releases Activity

Reduce the overhead of semop() by using the kernel stack instead of

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malloc'd memory to store the operations array if it is small enough
to fit.
This commit is contained in:
Tim J. Robbins 2003-12-19 13:07:17 +00:00
parent 22df7d650a
commit f5925b7436
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=123667
1 changed files with 11 additions and 4 deletions
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15
sys/kern/sysv_sem.c
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@ -877,6 +877,8 @@ semop(td, uap)
struct thread *td;
struct semop_args *uap;
{
#define SMALL_SOPS 8
struct sembuf small_sops[SMALL_SOPS];
int semid = uap->semid;
size_t nsops = uap->nsops;
struct sembuf *sops;
@ -900,16 +902,20 @@ semop(td, uap)
return (EINVAL);
/* Allocate memory for sem_ops */
if (nsops > seminfo.semopm) {
if (nsops <= SMALL_SOPS)
sops = small_sops;
else if (nsops <= seminfo.semopm)
sops = malloc(nsops * sizeof(*sops), M_TEMP, M_WAITOK);
else {
DPRINTF(("too many sops (max=%d, nsops=%d)\n", seminfo.semopm,
nsops));
return (E2BIG);
}
sops = malloc(nsops * sizeof(sops[0]), M_SEM, M_WAITOK);
if ((error = copyin(uap->sops, sops, nsops * sizeof(sops[0]))) != 0) {
DPRINTF(("error = %d from copyin(%08x, %08x, %d)\n", error,
uap->sops, sops, nsops * sizeof(sops[0])));
free(sops, M_SEM);
if (sops != small_sops)
free(sops, M_SEM);
return (error);
}
@ -1137,7 +1143,8 @@ semop(td, uap)
td->td_retval[0] = 0;
done2:
mtx_unlock(sema_mtxp);
free(sops, M_SEM);
if (sops != small_sops)
free(sops, M_SEM);
return (error);
}