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Index: sys/kern/vfs_vnops.c
===================================================================
--- sys/kern/vfs_vnops.c
+++ sys/kern/vfs_vnops.c
@@ -71,6 +71,7 @@
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/sx.h>
+#include <sys/sleepqueue.h>
#include <sys/sysctl.h>
#include <sys/ttycom.h>
#include <sys/conf.h>
@@ -667,8 +668,9 @@
off_t
foffset_lock(struct file *fp, int flags)
{
- struct mtx *mtxp;
+ volatile short *flagsp;
off_t res;
+ short state;
KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));
@@ -685,52 +687,63 @@
* According to McKusick the vn lock was protecting f_offset here.
* It is now protected by the FOFFSET_LOCKED flag.
*/
- mtxp = mtx_pool_find(mtxpool_sleep, fp);
- mtx_lock(mtxp);
- if ((flags & FOF_NOLOCK) == 0) {
- while (fp->f_vnread_flags & FOFFSET_LOCKED) {
- fp->f_vnread_flags |= FOFFSET_LOCK_WAITING;
- msleep(&fp->f_vnread_flags, mtxp, PUSER -1,
- "vofflock", 0);
+ flagsp = &fp->f_vnread_flags;
+ if (atomic_cmpset_acq_short(flagsp, 0, FOFFSET_LOCKED))
+ return (fp->f_offset);
+
+ sleepq_lock(&fp->f_vnread_flags);
+ state = *flagsp;
+ for (;;) {
+ if ((state & FOFFSET_LOCKED) == 0) {
+ if (!atomic_fcmpset_acq_short(flagsp, &state,
+ FOFFSET_LOCKED))
+ continue;
+ break;
+ }
+ if ((state & FOFFSET_LOCK_WAITING) == 0) {
+ if (!atomic_fcmpset_acq_short(flagsp, &state,
+ state | FOFFSET_LOCK_WAITING))
+ continue;
}
- fp->f_vnread_flags |= FOFFSET_LOCKED;
+ DROP_GIANT();
+ sleepq_add(&fp->f_vnread_flags, NULL, "vofflock", 0, 0);
+ sleepq_wait(&fp->f_vnread_flags, PUSER -1);
+ PICKUP_GIANT();
+ state = *flagsp;
}
res = fp->f_offset;
- mtx_unlock(mtxp);
+ sleepq_release(&fp->f_vnread_flags);
return (res);
}
void
foffset_unlock(struct file *fp, off_t val, int flags)
{
- struct mtx *mtxp;
+ volatile short *flagsp;
+ short state;
KASSERT((flags & FOF_OFFSET) == 0, ("FOF_OFFSET passed"));
-#if OFF_MAX <= LONG_MAX
- if ((flags & FOF_NOLOCK) != 0) {
- if ((flags & FOF_NOUPDATE) == 0)
- fp->f_offset = val;
- if ((flags & FOF_NEXTOFF) != 0)
- fp->f_nextoff = val;
- return;
- }
-#endif
-
- mtxp = mtx_pool_find(mtxpool_sleep, fp);
- mtx_lock(mtxp);
if ((flags & FOF_NOUPDATE) == 0)
fp->f_offset = val;
if ((flags & FOF_NEXTOFF) != 0)
fp->f_nextoff = val;
- if ((flags & FOF_NOLOCK) == 0) {
- KASSERT((fp->f_vnread_flags & FOFFSET_LOCKED) != 0,
- ("Lost FOFFSET_LOCKED"));
- if (fp->f_vnread_flags & FOFFSET_LOCK_WAITING)
- wakeup(&fp->f_vnread_flags);
- fp->f_vnread_flags = 0;
- }
- mtx_unlock(mtxp);
+
+ if ((flags & FOF_NOLOCK) != 0)
+ return;
+
+ flagsp = &fp->f_vnread_flags;
+ state = *flagsp;
+ if ((state & FOFFSET_LOCK_WAITING) == 0 &&
+ atomic_cmpset_rel_short(flagsp, state, 0))
+ return;
+
+ sleepq_lock(&fp->f_vnread_flags);
+ MPASS((fp->f_vnread_flags & FOFFSET_LOCKED) != 0);
+ MPASS((fp->f_vnread_flags & FOFFSET_LOCK_WAITING) != 0);
+ fp->f_vnread_flags = 0;
+ sleepq_broadcast(&fp->f_vnread_flags, SLEEPQ_SLEEP, 0, 0);
+ sleepq_release(&fp->f_vnread_flags);
}
void
Index: sys/sys/file.h
===================================================================
--- sys/sys/file.h
+++ sys/sys/file.h
@@ -156,7 +156,7 @@
* Below is the list of locks that protects members in struct file.
*
* (a) f_vnode lock required (shared allows both reads and writes)
- * (f) protected with mtx_lock(mtx_pool_find(fp))
+ * (f) updated with atomics and blocking on sleepq
* (d) cdevpriv_mtx
* none not locked
*/

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