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Subject[PATCH 10/11] Task watchers: Register semundo task watcher
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Date
This patch uses the task_watcher notifier chain to invoke exit_sem() at
appropriate times.

Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
--

ipc/sem.c | 23 +++++++++++++++++++++++
kernel/exit.c | 1 -
kernel/fork.c | 4 +---
3 files changed, 24 insertions(+), 4 deletions(-)

Index: linux-2.6.17-rc6-mm2/ipc/sem.c
===================================================================
--- linux-2.6.17-rc6-mm2.orig/ipc/sem.c
+++ linux-2.6.17-rc6-mm2/ipc/sem.c
@@ -82,10 +82,11 @@
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/seq_file.h>
#include <linux/mutex.h>
#include <linux/nsproxy.h>
+#include <linux/notifier.h>

#include <asm/uaccess.h>
#include "util.h"

#define sem_ids(ns) (*((ns)->ids[IPC_SEM_IDS]))
@@ -121,10 +122,31 @@ static int sysvipc_sem_proc_show(struct
#define sc_semmsl sem_ctls[0]
#define sc_semmns sem_ctls[1]
#define sc_semopm sem_ctls[2]
#define sc_semmni sem_ctls[3]

+static int sem_undo_task_exit(struct notifier_block *nb, unsigned long val,
+ void *t)
+{
+ switch(get_watch_event(val)) {
+ /*
+ * If it weren't for the fact that we need clone flags to call
+ * it we could also implement the copy_semundo portion of
+ * copy_process inside case WATCH_TASK_INIT
+ */
+ case WATCH_TASK_FREE:
+ exit_sem(t);
+ return NOTIFY_OK;
+ default: /* Don't care */
+ return NOTIFY_DONE;
+ }
+}
+
+static struct notifier_block sem_watch_tasks_nb = {
+ .notifier_call = sem_undo_task_exit
+};
+
static void __ipc_init __sem_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids)
{
ns->ids[IPC_SEM_IDS] = ids;
ns->sc_semmsl = SEMMSL;
ns->sc_semmns = SEMMNS;
@@ -171,10 +193,11 @@ void __init sem_init (void)
{
__sem_init_ns(&init_ipc_ns, &init_sem_ids);
ipc_init_proc_interface("sysvipc/sem",
" key semid perms nsems uid gid cuid cgid otime ctime\n",
IPC_SEM_IDS, sysvipc_sem_proc_show);
+ register_task_watcher(&sem_watch_tasks_nb);
}

/*
* Lockless wakeup algorithm:
* Without the check/retry algorithm a lockless wakeup is possible:
Index: linux-2.6.17-rc6-mm2/kernel/exit.c
===================================================================
--- linux-2.6.17-rc6-mm2.orig/kernel/exit.c
+++ linux-2.6.17-rc6-mm2/kernel/exit.c
@@ -919,11 +919,10 @@ fastcall NORET_TYPE void do_exit(long co
notify_result = notify_watchers(WATCH_TASK_FREE, tsk);
WARN_ON(notify_result & NOTIFY_STOP_MASK);

exit_mm(tsk);

- exit_sem(tsk);
__exit_files(tsk);
__exit_fs(tsk);
exit_task_namespaces(tsk);
exit_thread();
cpuset_exit(tsk);
Index: linux-2.6.17-rc6-mm2/kernel/fork.c
===================================================================
--- linux-2.6.17-rc6-mm2.orig/kernel/fork.c
+++ linux-2.6.17-rc6-mm2/kernel/fork.c
@@ -1089,11 +1089,11 @@ static task_t *copy_process(unsigned lon
goto bad_fork_cleanup_policy;
/* copy all the process information */
if ((retval = copy_semundo(clone_flags, p)))
goto bad_fork_cleanup_security;
if ((retval = copy_files(clone_flags, p)))
- goto bad_fork_cleanup_semundo;
+ goto bad_fork_cleanup_security;
if ((retval = copy_fs(clone_flags, p)))
goto bad_fork_cleanup_files;
if ((retval = copy_sighand(clone_flags, p)))
goto bad_fork_cleanup_fs;
if ((retval = copy_signal(clone_flags, p)))
@@ -1263,12 +1263,10 @@ bad_fork_cleanup_sighand:
__cleanup_sighand(p->sighand);
bad_fork_cleanup_fs:
exit_fs(p); /* blocking */
bad_fork_cleanup_files:
exit_files(p); /* blocking */
-bad_fork_cleanup_semundo:
- exit_sem(p);
bad_fork_cleanup_security:
security_task_free(p);
notify_result = notify_watchers(WATCH_TASK_FREE, p);
WARN_ON(notify_result & NOTIFY_STOP_MASK);
bad_fork_cleanup_policy:
--

-
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