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From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Subject: [PATCH] Make F_RDLCK/F_WRLCK atomic
lockf(LOCK_EX) would for instance drop any existing shared lock before taking
the exclusive lock. F_RDLCK/F_WRLCK need atomic changes, so introduce and use
__LOCK_ATOM
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
* misc/sys/file.h (__LOCK_ATOMIC): New macro.
* sysdeps/mach/hurd/fcntl.c (__libc_fcntl): Use __LOCK_ATOMIC along LOCK_SH and
LOCK_EX.
---
misc/sys/file.h | 1 +
sysdeps/mach/hurd/fcntl.c | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/misc/sys/file.h b/misc/sys/file.h
index 64e8764..a5892db 100644
--- a/misc/sys/file.h
+++ b/misc/sys/file.h
@@ -40,6 +40,7 @@ __BEGIN_DECLS
#define LOCK_SH 1 /* Shared lock. */
#define LOCK_EX 2 /* Exclusive lock. */
#define LOCK_UN 8 /* Unlock. */
+#define __LOCK_ATOMIC 16 /* Atomic update. */
/* Can be OR'd in to one of the above. */
#define LOCK_NB 4 /* Don't block when locking. */
diff --git a/sysdeps/mach/hurd/fcntl.c b/sysdeps/mach/hurd/fcntl.c
index 70180fa..8a8308f 100644
--- a/sysdeps/mach/hurd/fcntl.c
+++ b/sysdeps/mach/hurd/fcntl.c
@@ -150,8 +150,8 @@ __libc_fcntl (int fd, int cmd, ...)
}
switch (fl->l_type)
{
- case F_RDLCK: cmd |= LOCK_SH; break;
- case F_WRLCK: cmd |= LOCK_EX; break;
+ case F_RDLCK: cmd |= LOCK_SH | __LOCK_ATOMIC; break;
+ case F_WRLCK: cmd |= LOCK_EX | __LOCK_ATOMIC; break;
case F_UNLCK: cmd |= LOCK_UN; break;
default:
errno = EINVAL;
--
tg: (9a079e2..) t/WRLCK-upgrade (depends on: baseline)
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