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Rewrite the SMP filedesc locking in knote_attach() in order to

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1.  eliminate unnecessary loop which frees and re-allocates
	the just allocated array
  2.  eliminate the newsize recomputation
  3.  eliminate unnecessary unlock and relock around free
  4.  correctly match the free with the malloc into M_KQUEUE instead of M_TEMP
  5.  eliminate conditional assignment of oldlist, which is equivalent to a
	simple assignment
  6.  eliminate the oldlist temporary variable completely

Reviewed by:    jhb
This commit is contained in:
Jeffrey Hsu 2003-01-21 04:05:49 +00:00
parent 4273cc51a5
commit 34c54d9f74
1 changed files with 11 additions and 23 deletions
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34
sys/kern/kern_event.c
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@ -950,9 +950,9 @@ knote_fdclose(struct thread *td, int fd)
static void
knote_attach(struct knote *kn, struct filedesc *fdp)
{
struct klist *list, *oldlist, *tmp_knhash;
struct klist *list, *tmp_knhash;
u_long tmp_knhashmask;
int size, newsize;
int size;
FILEDESC_LOCK(fdp);
@ -966,9 +966,7 @@ knote_attach(struct knote *kn, struct filedesc *fdp)
fdp->fd_knhash = tmp_knhash;
fdp->fd_knhashmask = tmp_knhashmask;
} else {
FILEDESC_UNLOCK(fdp);
free(tmp_knhash, M_KQUEUE);
FILEDESC_LOCK(fdp);
}
}
list = &fdp->fd_knhash[KN_HASH(kn->kn_id, fdp->fd_knhashmask)];
@ -976,7 +974,6 @@ knote_attach(struct knote *kn, struct filedesc *fdp)
}
if (fdp->fd_knlistsize <= kn->kn_id) {
retry:
size = fdp->fd_knlistsize;
while (size <= kn->kn_id)
size += KQEXTENT;
@ -984,31 +981,22 @@ knote_attach(struct knote *kn, struct filedesc *fdp)
MALLOC(list, struct klist *,
size * sizeof(struct klist *), M_KQUEUE, M_WAITOK);
FILEDESC_LOCK(fdp);
newsize = fdp->fd_knlistsize;
while (newsize <= kn->kn_id)
newsize += KQEXTENT;
if (newsize != size) {
FILEDESC_UNLOCK(fdp);
free(list, M_TEMP);
FILEDESC_LOCK(fdp);
goto retry;
if (fdp->fd_knlistsize > kn->kn_id) {
FREE(list, M_KQUEUE);
goto bigenough;
}
if (fdp->fd_knlist != NULL) {
bcopy(fdp->fd_knlist, list,
fdp->fd_knlistsize * sizeof(struct klist *));
FREE(fdp->fd_knlist, M_KQUEUE);
}
bcopy(fdp->fd_knlist, list,
fdp->fd_knlistsize * sizeof(struct klist *));
bzero((caddr_t)list +
fdp->fd_knlistsize * sizeof(struct klist *),
(size - fdp->fd_knlistsize) * sizeof(struct klist *));
if (fdp->fd_knlist != NULL)
oldlist = fdp->fd_knlist;
else
oldlist = NULL;
fdp->fd_knlistsize = size;
fdp->fd_knlist = list;
FILEDESC_UNLOCK(fdp);
if (oldlist != NULL)
FREE(oldlist, M_KQUEUE);
FILEDESC_LOCK(fdp);
}
bigenough:
list = &fdp->fd_knlist[kn->kn_id];
done:
FILEDESC_UNLOCK(fdp);