Linus,
Please apply this patch. There are cases during which an application may
not want to wait (potentially) forever on a semaphore operation - it needs a
timeout. Oracle (DB) uses this sort of thing in Solaris to gain a few
percent in performance increases over the alternative (setting alarms to
interrupt semaphore operations). Other applications may find utility in this
added functionality as well - if you're using semaphores already, this is a
more portable solution to the problem than using timed futexes (semtimedop
works on sysv semaphores). As far as code goes, the amount of change is tiny
- this patch is so simple, it really ought to be a shoo-in...
--Mark
On Mon, Nov 25, 2002 at 05:25:54PM -0800, Mark Fasheh wrote:
> [ Ok, I'm an idiot. This is the proper patch - the previous one had some
> whitespace issues and left around a spare copy of util.c ]
>
> This patch adds a system call semtimedop which allows a program to execute a
> semaphore operation with a timeout. The function behaves just like semop
> except if the calling process has to be suspended. If the process has been
> suspended for longer than the timeout (and of course, its semaphore
> operation hasn't completed) then the system call returns EAGAIN to the
> calling process (via errno). Calling semtimedop with a NULL timeout is
> identical to calling semop.
>
> The overall impact to the semaphore code is minor.
>
> Userspace code to use/test this can be found at:
> http://www.exothermic.org/linux/semtimedop.tar.gz
> --Mark
diff -urNp linux-2.5.49-orig/arch/i386/kernel/sys_i386.c linux-2.5.49/arch/i386/kernel/sys_i386.c
--- linux-2.5.49-orig/arch/i386/kernel/sys_i386.c 2002-11-22 13:41:11.000000000 -0800
+++ linux-2.5.49/arch/i386/kernel/sys_i386.c 2002-11-22 17:28:35.000000000 -0800
@@ -140,7 +140,11 @@ asmlinkage int sys_ipc (uint call, int f
switch (call) {
case SEMOP:
- return sys_semop (first, (struct sembuf *)ptr, second);
+ return sys_semtimedop (first, (struct sembuf *)ptr, second, NULL);
+ case SEMTIMEDOP:
+ return sys_semtimedop (first, (struct sembuf *)ptr, second,
+ (const struct timespec *)fifth);
+
case SEMGET:
return sys_semget (first, second, third);
case SEMCTL: {
diff -urNp linux-2.5.49-orig/arch/ia64/ia32/sys_ia32.c linux-2.5.49/arch/ia64/ia32/sys_ia32.c
--- linux-2.5.49-orig/arch/ia64/ia32/sys_ia32.c 2002-11-22 13:40:49.000000000 -0800
+++ linux-2.5.49/arch/ia64/ia32/sys_ia32.c 2002-11-22 17:28:35.000000000 -0800
@@ -2124,6 +2124,7 @@ struct ipc_kludge {
#define SEMOP 1
#define SEMGET 2
#define SEMCTL 3
+#define SEMTIMEDOP 4
#define MSGSND 11
#define MSGRCV 12
#define MSGGET 13
diff -urNp linux-2.5.49-orig/arch/ia64/kernel/entry.S linux-2.5.49/arch/ia64/kernel/entry.S
--- linux-2.5.49-orig/arch/ia64/kernel/entry.S 2002-11-22 13:40:24.000000000 -0800
+++ linux-2.5.49/arch/ia64/kernel/entry.S 2002-11-22 17:28:35.000000000 -0800
@@ -1254,7 +1254,7 @@ sys_call_table:
data8 sys_epoll_create
data8 sys_epoll_ctl
data8 sys_epoll_wait // 1245
- data8 ia64_ni_syscall
+ data8 sys_semtimedop
data8 ia64_ni_syscall
data8 ia64_ni_syscall
data8 ia64_ni_syscall
diff -urNp linux-2.5.49-orig/include/asm-i386/ipc.h linux-2.5.49/include/asm-i386/ipc.h
--- linux-2.5.49-orig/include/asm-i386/ipc.h 2002-11-22 13:40:58.000000000 -0800
+++ linux-2.5.49/include/asm-i386/ipc.h 2002-11-22 17:28:36.000000000 -0800
@@ -14,6 +14,7 @@ struct ipc_kludge {
#define SEMOP 1
#define SEMGET 2
#define SEMCTL 3
+#define SEMTIMEDOP 4
#define MSGSND 11
#define MSGRCV 12
#define MSGGET 13
diff -urNp linux-2.5.49-orig/include/asm-ia64/unistd.h linux-2.5.49/include/asm-ia64/unistd.h
--- linux-2.5.49-orig/include/asm-ia64/unistd.h 2002-11-22 13:40:19.000000000 -0800
+++ linux-2.5.49/include/asm-ia64/unistd.h 2002-11-22 17:28:36.000000000 -0800
@@ -235,6 +235,7 @@
#define __NR_epoll_create 1243
#define __NR_epoll_ctl 1244
#define __NR_epoll_wait 1245
+#define __NR_semtimedop 1246
#if !defined(__ASSEMBLY__) && !defined(ASSEMBLER)
diff -urNp linux-2.5.49-orig/include/linux/sem.h linux-2.5.49/include/linux/sem.h
--- linux-2.5.49-orig/include/linux/sem.h 2002-11-22 13:40:39.000000000 -0800
+++ linux-2.5.49/include/linux/sem.h 2002-11-22 17:28:36.000000000 -0800
@@ -140,6 +140,8 @@ struct sysv_sem {
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);
+asmlinkage long sys_semtimedop (int semid, struct sembuf *sops,
+ unsigned nsops, const struct timespec *timeout);
#endif /* __KERNEL__ */
diff -urNp linux-2.5.49-orig/ipc/sem.c linux-2.5.49/ipc/sem.c
--- linux-2.5.49-orig/ipc/sem.c 2002-11-22 13:40:29.000000000 -0800
+++ linux-2.5.49/ipc/sem.c 2002-11-25 17:08:32.000000000 -0800
@@ -62,6 +62,7 @@
#include <linux/spinlock.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
+#include <linux/time.h>
#include <linux/smp_lock.h>
#include <linux/security.h>
#include <asm/uaccess.h>
@@ -969,6 +970,12 @@ static int alloc_undo(struct sem_array *
asmlinkage long sys_semop (int semid, struct sembuf *tsops, unsigned nsops)
{
+ return sys_semtimedop(semid, tsops, nsops, NULL);
+}
+
+asmlinkage long sys_semtimedop (int semid, struct sembuf *tsops,
+ unsigned nsops, const struct timespec *timeout)
+{
int error = -EINVAL;
struct sem_array *sma;
struct sembuf fast_sops[SEMOPM_FAST];
@@ -976,6 +983,7 @@ asmlinkage long sys_semop (int semid, st
struct sem_undo *un;
int undos = 0, decrease = 0, alter = 0;
struct sem_queue queue;
+ unsigned long offset = MAX_SCHEDULE_TIMEOUT;
if (nsops < 1 || semid < 0)
@@ -991,6 +999,19 @@ asmlinkage long sys_semop (int semid, st
error=-EFAULT;
goto out_free;
}
+ if (timeout) {
+ struct timespec _timeout;
+ if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
+ error = -EFAULT;
+ goto out_free;
+ }
+ if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
+ _timeout.tv_nsec >= 1000000000L) {
+ error = -EINVAL;
+ goto out_free;
+ }
+ offset = timespec_to_jiffies(&_timeout);
+ }
lock_semundo();
sma = sem_lock(semid);
error=-EINVAL;
@@ -1058,7 +1079,7 @@ asmlinkage long sys_semop (int semid, st
sem_unlock(sma);
unlock_semundo();
- schedule();
+ offset = schedule_timeout(offset);
lock_semundo();
sma = sem_lock(semid);
@@ -1084,6 +1105,8 @@ asmlinkage long sys_semop (int semid, st
break;
} else {
error = queue.status;
+ if (error == -EINTR && offset == 0)
+ error = -EAGAIN;
if (queue.prev) /* got Interrupt */
break;
/* Everything done by update_queue */
diff -urNp linux-2.5.49-orig/ipc/util.c linux-2.5.49/ipc/util.c
--- linux-2.5.49-orig/ipc/util.c 2002-11-22 13:40:39.000000000 -0800
+++ linux-2.5.49/ipc/util.c 2002-11-22 17:28:36.000000000 -0800
@@ -538,6 +538,13 @@ asmlinkage long sys_semop (int semid, st
return -ENOSYS;
}
+asmlinkage long sys_semtimedop (int semid, struct sembuf *sops, unsigned nsops,
+ const struct timespec *timeout)
+{
+ return -ENOSYS;
+}
+
+
asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
{
return -ENOSYS;
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sat Nov 30 2002 - 22:00:15 EST