From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Thu, 29 Mar 2018 19:47:29 +0000 (+0100)
Subject: Make F_RDLCK/F_WRLCK atomic
X-Git-Tag: archive/raspbian/2.27-3+rpi1^2~82
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=74ba0e6030f501bb80c522d9eaca5874489c9f62;p=glibc.git

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.


Gbp-Pq: Topic hurd-i386
Gbp-Pq: Name tg-WRLCK-upgrade.diff
---

diff --git a/misc/sys/file.h b/misc/sys/file.h
index 86abfa18d..e6494fa33 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 0b231645c..533e659ea 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;