[PATCH] 2.5.9 SEM_UNDO patch

As we discussed some time ago, here is a patch for the SEM_UNDO change
that can be applied to linux-2.5.9.

include/linux/sched.h

@@ -45,6 +45,7 @@ struct exec_domain;
 #define CLONE_PARENT	0x00008000	/* set if we want to have the same parent as the cloner */
 #define CLONE_THREAD	0x00010000	/* Same thread group? */
 #define CLONE_NEWNS	0x00020000	/* New namespace group? */
+#define CLONE_SYSVSEM	0x00040000	/* share system V SEM_UNDO semantics */
 
 #define CLONE_SIGNAL	(CLONE_SIGHAND | CLONE_THREAD)
 
@@ -315,8 +316,7 @@ struct task_struct {
 	struct tty_struct *tty; /* NULL if no tty */
 	unsigned int locks; /* How many file locks are being held */
 /* ipc stuff */
-	struct sem_undo *semundo;
-	struct sem_queue *semsleeping;
+	struct sysv_sem sysvsem;
 /* CPU-specific state of this task */
 	struct thread_struct thread;
 /* filesystem information */

include/linux/sem.h

@@ -121,6 +121,21 @@ struct sem_undo {
 	short *			semadj;		/* array of adjustments, one per semaphore */
 };
 
+/* sem_undo_list controls shared access to the list of sem_undo structures
+ * that may be shared among all a CLONE_SYSVSEM task group.
+ */ 
+struct sem_undo_list {
+	atomic_t	refcnt;
+	spinlock_t	lock;
+	volatile unsigned long	add_count;
+	struct sem_undo	*proc_list;
+};
+
+struct sysv_sem {
+	struct sem_undo_list *undo_list;
+	struct sem_queue *sleep_list;
+};
+
 asmlinkage long sys_semget (key_t key, int nsems, int semflg);
 asmlinkage long sys_semop (int semid, struct sembuf *sops, unsigned nsops);
 asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg);

ipc/util.c

@@ -340,6 +340,17 @@ int ipc_parse_version (int *cmd)
  * Dummy functions when SYSV IPC isn't configured
  */
 
+int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
+{
+	return 0;
+}
+
+void exit_semundo(struct task_struct *tsk)
+{
+	return;
+}
+
+
 void sem_exit (void)
 {
     return;

kernel/fork.c

@@ -34,6 +34,9 @@
 
 static kmem_cache_t *task_struct_cachep;
 
+extern int copy_semundo(unsigned long clone_flags, struct task_struct *tsk);
+extern void exit_semundo(struct task_struct *tsk);
+
 /* The idle threads do not count.. */
 int nr_threads;
 
@@ -710,8 +713,10 @@ int do_fork(unsigned long clone_flags, unsigned long stack_start,
 
 	retval = -ENOMEM;
 	/* copy all the process information */
-	if (copy_files(clone_flags, p))
+	if (copy_semundo(clone_flags, p))
 		goto bad_fork_cleanup;
+	if (copy_files(clone_flags, p))
+		goto bad_fork_cleanup_semundo;
 	if (copy_fs(clone_flags, p))
 		goto bad_fork_cleanup_files;
 	if (copy_sighand(clone_flags, p))
@@ -723,7 +728,6 @@ int do_fork(unsigned long clone_flags, unsigned long stack_start,
 	retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
 	if (retval)
 		goto bad_fork_cleanup_namespace;
-	p->semundo = NULL;
 	
 	/* Our parent execution domain becomes current domain
 	   These must match for thread signalling to apply */
@@ -815,6 +819,8 @@ int do_fork(unsigned long clone_flags, unsigned long stack_start,
 	exit_fs(p); /* blocking */
 bad_fork_cleanup_files:
 	exit_files(p); /* blocking */
+bad_fork_cleanup_semundo:
+	exit_semundo(p);
 bad_fork_cleanup:
 	put_exec_domain(p->thread_info->exec_domain);
 	if (p->binfmt && p->binfmt->module)