From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Tue, 23 Apr 2024 16:23:00 +0000 (+0300)
Subject: [PATCH] Make F_RDLCK/F_WRLCK atomic
X-Git-Tag: archive/raspbian/2.28-10+rpi1+deb10u3^2~75
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=c87967c0148458199e00cb266f3cea0ff452950f;p=glibc.git

[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.

XXX: Adding to misc/sys/file.h is questionable


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/f_setlk.c b/sysdeps/mach/hurd/f_setlk.c
index edfb292db..27f7d2729 100644
--- a/sysdeps/mach/hurd/f_setlk.c
+++ b/sysdeps/mach/hurd/f_setlk.c
@@ -35,8 +35,8 @@ __f_setlk (int fd, int type, int whence, __off64_t start, __off64_t len, int wai
 
   switch (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;