From: Samuel Thibault 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 * 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)