2.5.75

 ipc

diff -Nru a/ipc/sem.c b/ipc/sem.c
--- a/ipc/sem.c   Thu Jul 10 13:16:27 2003
+++ b/ipc/sem.c   Thu Jul 10 13:16:27 2003
@@ -49,6 +49,10 @@
  *      increase. If there are decrement operations in the operations
  *      array we do the same as before.
  *
+ * With the incarnation of O(1) scheduler, it becomes unnecessary to perform
+ * check/retry algorithm for waking up blocked processes as the new scheduler
+ * is better at handling thread switch than the old one.
+ *
  * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
  *
  * SMP-threaded, sysctl's added
@@ -258,8 +262,7 @@
  */
 
 static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
-              int nsops, struct sem_undo *un, int pid,
-              int do_undo)
+              int nsops, struct sem_undo *un, int pid)
 {
    int result, sem_op;
    struct sembuf *sop;
@@ -289,10 +292,6 @@
       curr->semval = result;
    }
 
-   if (do_undo) {
-      result = 0;
-      goto undo;
-   }
    sop--;
    while (sop >= sops) {
       sma->sem_base[sop->sem_num].sempid = pid;
@@ -334,23 +333,14 @@
 
    for (q = sma->sem_pending; q; q = q->next) {
          
-      if (q->status == 1)
-         continue;   /* this one was woken up before */
-
       error = try_atomic_semop(sma, q->sops, q->nsops,
-                q->undo, q->pid, q->alter);
+                q->undo, q->pid);
 
       /* Does q->sleeper still need to sleep? */
       if (error <= 0) {
-            /* Found one, wake it up */
-         wake_up_process(q->sleeper);
-         if (error == 0 && q->alter) {
-            /* if q-> alter let it self try */
-            q->status = 1;
-            return;
-         }
          q->status = error;
          remove_from_queue(sma,q);
+         wake_up_process(q->sleeper);
       }
    }
 }
@@ -1062,7 +1052,7 @@
    if (error)
       goto out_unlock_free;
 
-   error = try_atomic_semop (sma, sops, nsops, un, current->pid, 0);
+   error = try_atomic_semop (sma, sops, nsops, un, current->pid);
    if (error <= 0)
       goto update;
 
@@ -1075,55 +1065,46 @@
    queue.nsops = nsops;
    queue.undo = un;
    queue.pid = current->pid;
-   queue.alter = decrease;
    queue.id = semid;
    if (alter)
       append_to_queue(sma ,&queue);
    else
       prepend_to_queue(sma ,&queue);
 
-   for (;;) {
-      queue.status = -EINTR;
-      queue.sleeper = current;
-      current->state = TASK_INTERRUPTIBLE;
-      sem_unlock(sma);
+   queue.status = -EINTR;
+   queue.sleeper = current;
+   current->state = TASK_INTERRUPTIBLE;
+   sem_unlock(sma);
 
-      if (timeout)
-         jiffies_left = schedule_timeout(jiffies_left);
-      else
-         schedule();
+   if (timeout)
+      jiffies_left = schedule_timeout(jiffies_left);
+   else
+      schedule();
 
-      sma = sem_lock(semid);
-      if(sma==NULL) {
-         if(queue.prev != NULL)
-            BUG();
-         error = -EIDRM;
-         goto out_free;
-      }
-      /*
-       * If queue.status == 1 we where woken up and
-       * have to retry else we simply return.
-       * If an interrupt occurred we have to clean up the
-       * queue
-       *
-       */
-      if (queue.status == 1)
-      {
-         error = try_atomic_semop (sma, sops, nsops, un,
-                    current->pid,0);
-         if (error <= 0) 
-            break;
-      } else {
-         error = queue.status;
-         if (error == -EINTR && timeout && jiffies_left == 0)
-            error = -EAGAIN;
-         if (queue.prev) /* got Interrupt */
-            break;
-         /* Everything done by update_queue */
-         goto out_unlock_free;
-      }
+   sma = sem_lock(semid);
+   if(sma==NULL) {
+      if(queue.prev != NULL)
+         BUG();
+      error = -EIDRM;
+      goto out_free;
+   }
+
+   /*
+    * If queue.status != -EINTR we are woken up by another process
+    */
+   error = queue.status;
+   if (queue.status != -EINTR) {
+      goto out_unlock_free;
    }
+
+   /*
+    * If an interrupt occurred we have to clean up the queue
+    */
+   if (timeout && jiffies_left == 0)
+      error = -EAGAIN;
    remove_from_queue(sma,&queue);
+   goto out_unlock_free;
+
 update:
    if (alter)
       update_queue (sma);