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Subject[PATCH] 2.5.49 - semaphore operations with timeouts
[ 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;
-
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