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Avoid acquiring Giant for some common light-weight or already MPSAFE

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fcntl() operations, including:

  F_DUPFD          dup() alias
  F_GETFD          retrieve close-on-exec flag
  F_SETFD          set close-on-exec flag
  F_GETFL          retrieve file descriptor flags

For the remaining fcntl() operations, do acquire Giant, especially
where we call into fo_ioctl() as a result.  We're not yet ready to
push Giant into fo_ioctl().  Once we do, this can all become quite a
bit prettier.
This commit is contained in:
Robert Watson 2004-08-06 22:00:55 +00:00
parent f6b61a6442
commit a0a819747c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=133232
1 changed files with 31 additions and 2 deletions
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33
sys/kern/kern_descrip.c
View file

@ -333,12 +333,29 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
struct vnode *vp;
u_int newmin;
int error, flg, tmp;
int giant_locked;
/*
* XXXRW: Some fcntl() calls require Giant -- others don't. Try to
* avoid grabbing Giant for calls we know don't need it.
*/
switch (cmd) {
case F_DUPFD:
case F_GETFD:
case F_SETFD:
case F_GETFL:
giant_locked = 0;
break;
default:
giant_locked = 1;
mtx_lock(&Giant);
}
error = 0;
flg = F_POSIX;
p = td->td_proc;
fdp = p->p_fd;
mtx_lock(&Giant);
FILEDESC_LOCK(fdp);
if ((unsigned)fd >= fdp->fd_nfiles ||
(fp = fdp->fd_ofiles[fd]) == NULL) {
@ -350,6 +367,7 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
switch (cmd) {
case F_DUPFD:
mtx_assert(&Giant, MA_NOTOWNED);
FILEDESC_UNLOCK(fdp);
newmin = arg;
PROC_LOCK(p);
@ -364,17 +382,21 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
break;
case F_GETFD:
mtx_assert(&Giant, MA_NOTOWNED);
td->td_retval[0] = (*pop & UF_EXCLOSE) ? FD_CLOEXEC : 0;
FILEDESC_UNLOCK(fdp);
break;
case F_SETFD:
mtx_assert(&Giant, MA_NOTOWNED);
*pop = (*pop &~ UF_EXCLOSE) |
(arg & FD_CLOEXEC ? UF_EXCLOSE : 0);
FILEDESC_UNLOCK(fdp);
break;
case F_GETFL:
/* MPSAFE */
mtx_assert(&Giant, MA_NOTOWNED);
FILE_LOCK(fp);
FILEDESC_UNLOCK(fdp);
td->td_retval[0] = OFLAGS(fp->f_flag);
@ -382,6 +404,7 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
break;
case F_SETFL:
mtx_assert(&Giant, MA_OWNED);
FILE_LOCK(fp);
FILEDESC_UNLOCK(fdp);
fhold_locked(fp);
@ -409,6 +432,7 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
break;
case F_GETOWN:
mtx_assert(&Giant, MA_OWNED);
fhold(fp);
FILEDESC_UNLOCK(fdp);
error = fo_ioctl(fp, FIOGETOWN, &tmp, td->td_ucred, td);
@ -418,6 +442,7 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
break;
case F_SETOWN:
mtx_assert(&Giant, MA_OWNED);
fhold(fp);
FILEDESC_UNLOCK(fdp);
tmp = arg;
@ -426,10 +451,12 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
break;
case F_SETLKW:
mtx_assert(&Giant, MA_OWNED);
flg |= F_WAIT;
/* FALLTHROUGH F_SETLK */
case F_SETLK:
mtx_assert(&Giant, MA_OWNED);
if (fp->f_type != DTYPE_VNODE) {
FILEDESC_UNLOCK(fdp);
error = EBADF;
@ -503,6 +530,7 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
break;
case F_GETLK:
mtx_assert(&Giant, MA_OWNED);
if (fp->f_type != DTYPE_VNODE) {
FILEDESC_UNLOCK(fdp);
error = EBADF;
@ -542,7 +570,8 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
break;
}
done2:
mtx_unlock(&Giant);
if (giant_locked)
mtx_unlock(&Giant);
return (error);
}