[PATCH 3/9] Task Watchers v2: Register semundo task watcher

Matt Helsley
2006-11-03T04:23:00Z

[-- Attachment #1: task-watchers-register-semundo --]
[-- Type: text/plain, Size: 7490 bytes --]

Make the semaphore undo code use a task watcher instead of hooking into
copy_process() and do_exit() directly.

Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
---
include/linux/sem.h | 17 -----------------
ipc/sem.c | 12 ++++++++----
kernel/exit.c | 3 ---
kernel/fork.c | 6 +-----
4 files changed, 9 insertions(+), 29 deletions(-)

Benchmark results:
System: 4 1.7GHz ppc64 (Power 4+) processors, 30968600MB RAM, 2.6.19-rc2-mm2 kernel

Clone Number of Children Cloned
5000 7500 10000 12500 15000 17500
---------------------------------------------------------------------------------------
Mean 17960.5 18169.3 18408.2 18479.9 18515.6 18465.4
Dev 305.381 314.209 292.395 284.992 299.331 295.311
Err (%) 1.70029 1.72934 1.5884 1.54217 1.61664 1.59927

Fork Number of Children Forked
5000 7500 10000 12500 15000 17500
---------------------------------------------------------------------------------------
Mean 18050.2 18141.4 18316.2 18386.2 18441.9 18476.2
Dev 295.68 312.922 296.962 298.81 300.985 294.046
Err (%) 1.63809 1.72491 1.62131 1.62519 1.63207 1.59149

Kernbench:
Elapsed: 124.272s User: 439.643s System: 46.32s CPU: 390.5%
439.64user 46.25system 2:04.46elapsed 390%CPU (0avgtext+0avgdata 0maxresident)k
439.70user 46.27system 2:04.04elapsed 391%CPU (0avgtext+0avgdata 0maxresident)k
439.64user 46.31system 2:04.18elapsed 391%CPU (0avgtext+0avgdata 0maxresident)k
439.49user 46.27system 2:04.41elapsed 390%CPU (0avgtext+0avgdata 0maxresident)k
439.55user 46.47system 2:04.32elapsed 390%CPU (0avgtext+0avgdata 0maxresident)k
439.77user 46.29system 2:04.63elapsed 390%CPU (0avgtext+0avgdata 0maxresident)k
439.61user 46.31system 2:04.09elapsed 391%CPU (0avgtext+0avgdata 0maxresident)k
439.68user 46.31system 2:04.02elapsed 391%CPU (0avgtext+0avgdata 0maxresident)k
439.76user 46.49system 2:04.59elapsed 390%CPU (0avgtext+0avgdata 0maxresident)k
439.59user 46.23system 2:03.98elapsed 391%CPU (0avgtext+0avgdata 0maxresident)k

Index: linux-2.6.19-rc2-mm2/ipc/sem.c
===================================================================
--- linux-2.6.19-rc2-mm2.orig/ipc/sem.c
+++ linux-2.6.19-rc2-mm2/ipc/sem.c
@@ -81,10 +81,11 @@
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/seq_file.h>
#include <linux/mutex.h>
#include <linux/nsproxy.h>
+#include <linux/task_watchers.h>

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

#define sem_ids(ns) (*((ns)->ids[IPC_SEM_IDS]))
@@ -1288,11 +1289,11 @@ asmlinkage long sys_semop (int semid, st
* See the notes above unlock_semundo() regarding the spin_lock_init()
* in this code. Initialize the undo_list->lock here instead of get_undo_list()
* because of the reasoning in the comment above unlock_semundo.
*/

-int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
+static int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
{
struct sem_undo_list *undo_list;
int error;

if (clone_flags & CLONE_SYSVSEM) {
@@ -1304,10 +1305,11 @@ int copy_semundo(unsigned long clone_fla
} else
tsk->sysvsem.undo_list = NULL;

return 0;
}
+task_watcher_func(init, copy_semundo);

/*
* add semadj values to semaphores, free undo structures.
* undo structures are not freed when semaphore arrays are destroyed
* so some of them may be out of date.
@@ -1317,22 +1319,22 @@ int copy_semundo(unsigned long clone_fla
* should we queue up and wait until we can do so legally?
* The original implementation attempted to do this (queue and wait).
* The current implementation does not do so. The POSIX standard
* and SVID should be consulted to determine what behavior is mandated.
*/
-void exit_sem(struct task_struct *tsk)
+static int exit_sem(unsigned long ignored, struct task_struct *tsk)
{
struct sem_undo_list *undo_list;
struct sem_undo *u, **up;
struct ipc_namespace *ns;

undo_list = tsk->sysvsem.undo_list;
if (!undo_list)
- return;
+ return 0;

if (!atomic_dec_and_test(&undo_list->refcnt))
- return;
+ return 0;

ns = tsk->nsproxy->ipc_ns;
/* There's no need to hold the semundo list lock, as current
* is the last task exiting for this undo list.
*/
@@ -1395,11 +1397,13 @@ found:
update_queue(sma);
next_entry:
sem_unlock(sma);
}
kfree(undo_list);
+ return 0;
}
+task_watcher_func(free, exit_sem);

#ifdef CONFIG_PROC_FS
static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
{
struct sem_array *sma = it;
Index: linux-2.6.19-rc2-mm2/kernel/exit.c
===================================================================
--- linux-2.6.19-rc2-mm2.orig/kernel/exit.c
+++ linux-2.6.19-rc2-mm2/kernel/exit.c
@@ -46,12 +46,10 @@
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

-extern void sem_exit (void);
-
static void exit_mm(struct task_struct * tsk);

static void __unhash_process(struct task_struct *p)
{
nr_threads--;
@@ -919,11 +917,10 @@ fastcall NORET_TYPE void do_exit(long co
exit_mm(tsk);
notify_task_watchers(WATCH_TASK_FREE, code, tsk);

if (group_dead)
acct_process();
- exit_sem(tsk);
__exit_files(tsk);
__exit_fs(tsk);
exit_thread();
cpuset_exit(tsk);
exit_keys(tsk);
Index: linux-2.6.19-rc2-mm2/kernel/fork.c
===================================================================
--- linux-2.6.19-rc2-mm2.orig/kernel/fork.c
+++ linux-2.6.19-rc2-mm2/kernel/fork.c
@@ -1095,14 +1095,12 @@ static struct task_struct *copy_process(
#endif

if ((retval = security_task_alloc(p)))
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)))
@@ -1269,12 +1267,10 @@ 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);
bad_fork_cleanup_policy:
#ifdef CONFIG_NUMA
mpol_free(p->mempolicy);
Index: linux-2.6.19-rc2-mm2/include/linux/sem.h
===================================================================
--- linux-2.6.19-rc2-mm2.orig/include/linux/sem.h
+++ linux-2.6.19-rc2-mm2/include/linux/sem.h
@@ -136,25 +136,8 @@ struct sem_undo_list {

struct sysv_sem {
struct sem_undo_list *undo_list;
};

-#ifdef CONFIG_SYSVIPC
-
-extern int copy_semundo(unsigned long clone_flags, struct task_struct *tsk);
-extern void exit_sem(struct task_struct *tsk);
-
-#else
-static inline int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
-{
- return 0;
-}
-
-static inline void exit_sem(struct task_struct *tsk)
-{
- return;
-}
-#endif
-
#endif /* __KERNEL__ */

#endif /* _LINUX_SEM_H */