ipc/sem.c: add a per-semaphore pending list

Based on Nick's findings:

sysv sem has the concept of semaphore arrays that consist out of multiple
semaphores.  Atomic operations that affect multiple semaphores are
supported.

The patch is the first step for optimizing simple, single semaphore
operations: In addition to the global list of all pending operations, a
2nd, per-semaphore list with the simple operations is added.

Note: this patch does not make sense by itself, the new list is used
nowhere.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Pierre Peiffer <peifferp@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/linux/sem.h b/include/linux/sem.h
index 1b191c176bcd..8a4adbef8a0f 100644
--- a/include/linux/sem.h
+++ b/include/linux/sem.h
@@ -86,6 +86,7 @@ struct task_struct;
 struct sem {
         int     semval;         /* current value */
         int     sempid;         /* pid of last operation */
+        struct list_head sem_pending; /* pending single-sop operations */
 };
 
 /* One sem_array data structure for each set of semaphores in the system. */
@@ -96,11 +97,13 @@ struct sem_array {
         struct sem              *sem_base;      /* ptr to first semaphore in array */
         struct list_head        sem_pending;    /* pending operations to be processed */
         struct list_head        list_id;        /* undo requests on this array */
-        unsigned long           sem_nsems;      /* no. of semaphores in array */
+        int                     sem_nsems;      /* no. of semaphores in array */
+        int                     complex_count;  /* pending complex operations */
 };
 
 /* One queue for each sleeping process in the system. */
 struct sem_queue {
+        struct list_head        simple_list; /* queue of pending operations */
         struct list_head        list;    /* queue of pending operations */
         struct task_struct      *sleeper; /* this process */
         struct sem_undo         *undo;   /* undo structure */