Hi,
On a UP machine loads and stores should appear in program order so we
dont need most memory barriers. Convert a number of ?mb() etc to smp_?mb()
so we only take a hit on SMP builds.
What do people think of this patch?
Thinking some more about this, perhaps we should remove the ?mb() barriers
and instead have only io_?mb() and smp_?mb(). This has the advantage of
making it clear what barriers should be used in drivers to order
cacheable and non cacheable memory (a problem on ppc/ppc64 at least).
diff -puN fs/buffer.c~barrier_rework_2 fs/buffer.c
--- foobar2/fs/buffer.c~barrier_rework_2 2005-03-21 12:01:06.773011661
+1100
+++ foobar2-anton/fs/buffer.c 2005-03-21 12:01:06.848005928 +1100
@@ -218,7 +218,7 @@ struct super_block *freeze_bdev(struct b
sb = get_super(bdev);
if (sb && !(sb->s_flags & MS_RDONLY)) {
sb->s_frozen = SB_FREEZE_WRITE;
- wmb();
+ smp_wmb();
sync_inodes_sb(sb, 0);
DQUOT_SYNC(sb);
@@ -235,7 +235,7 @@ struct super_block *freeze_bdev(struct b
sync_inodes_sb(sb, 1);
sb->s_frozen = SB_FREEZE_TRANS;
- wmb();
+ smp_wmb();
sync_blockdev(sb->s_bdev);
@@ -263,7 +263,7 @@ void thaw_bdev(struct block_device *bdev
if (sb->s_op->unlockfs)
sb->s_op->unlockfs(sb);
sb->s_frozen = SB_UNFROZEN;
- wmb();
+ smp_wmb();
wake_up(&sb->s_wait_unfrozen);
drop_super(sb);
}
diff -puN ipc/mqueue.c~barrier_rework_2 ipc/mqueue.c
--- foobar2/ipc/mqueue.c~barrier_rework_2 2005-03-21 12:01:06.779011202
+1100
+++ foobar2-anton/ipc/mqueue.c 2005-03-21 12:01:06.851005699 +1100
@@ -767,7 +767,7 @@ static inline void pipelined_send(struct
list_del(&receiver->list);
receiver->state = STATE_PENDING;
wake_up_process(receiver->task);
- wmb();
+ smp_wmb();
receiver->state = STATE_READY;
}
@@ -786,7 +786,7 @@ static inline void pipelined_receive(str
list_del(&sender->list);
sender->state = STATE_PENDING;
wake_up_process(sender->task);
- wmb();
+ smp_wmb();
sender->state = STATE_READY;
}
diff -puN kernel/kthread.c~barrier_rework_2 kernel/kthread.c
--- foobar2/kernel/kthread.c~barrier_rework_2 2005-03-21 12:01:06.784010820
+1100
+++ foobar2-anton/kernel/kthread.c 2005-03-21 12:01:06.853005546 +1100
@@ -174,7 +174,7 @@ int kthread_stop(struct task_struct *k)
/* Must init completion *before* thread sees kthread_stop_info.k */
init_completion(&kthread_stop_info.done);
- wmb();
+ smp_wmb();
/* Now set kthread_should_stop() to true, and wake it up. */
kthread_stop_info.k = k;
diff -puN kernel/profile.c~barrier_rework_2 kernel/profile.c
--- foobar2/kernel/profile.c~barrier_rework_2 2005-03-21 12:01:06.790010361
+1100
+++ foobar2-anton/kernel/profile.c 2005-03-21 12:01:06.855005393 +1100
@@ -528,7 +528,7 @@ static int __init create_hash_tables(voi
return 0;
out_cleanup:
prof_on = 0;
- mb();
+ smp_mb();
on_each_cpu(profile_nop, NULL, 0, 1);
for_each_online_cpu(cpu) {
struct page *page;
diff -puN kernel/ptrace.c~barrier_rework_2 kernel/ptrace.c
--- foobar2/kernel/ptrace.c~barrier_rework_2 2005-03-21 12:01:06.795009979
+1100
+++ foobar2-anton/kernel/ptrace.c 2005-03-21 12:01:06.856005316 +1100
@@ -135,7 +135,7 @@ int ptrace_attach(struct task_struct *ta
(current->gid != task->sgid) ||
(current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
goto bad;
- rmb();
+ smp_rmb();
if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
goto bad;
/* the same process cannot be attached many times */
diff -puN kernel/stop_machine.c~barrier_rework_2 kernel/stop_machine.c
--- foobar2/kernel/stop_machine.c~barrier_rework_2 2005-03-21
12:01:06.800009597 +1100
+++ foobar2-anton/kernel/stop_machine.c 2005-03-21 12:01:06.858005164 +1100
@@ -32,7 +32,7 @@ static int stopmachine(void *cpu)
set_cpus_allowed(current, cpumask_of_cpu((int)(long)cpu));
/* Ack: we are alive */
- mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
+ smp_mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
atomic_inc(&stopmachine_thread_ack);
/* Simple state machine */
@@ -42,14 +42,14 @@ static int stopmachine(void *cpu)
local_irq_disable();
irqs_disabled = 1;
/* Ack: irqs disabled. */
- mb(); /* Must read state first. */
+ smp_mb(); /* Must read state first. */
atomic_inc(&stopmachine_thread_ack);
} else if (stopmachine_state == STOPMACHINE_PREPARE
&& !prepared) {
/* Everyone is in place, hold CPU. */
preempt_disable();
prepared = 1;
- mb(); /* Must read state first. */
+ smp_mb(); /* Must read state first. */
atomic_inc(&stopmachine_thread_ack);
}
/* Yield in first stage: migration threads need to
@@ -61,7 +61,7 @@ static int stopmachine(void *cpu)
}
/* Ack: we are exiting. */
- mb(); /* Must read state first. */
+ smp_mb(); /* Must read state first. */
atomic_inc(&stopmachine_thread_ack);
if (irqs_disabled)
@@ -76,7 +76,7 @@ static int stopmachine(void *cpu)
static void stopmachine_set_state(enum stopmachine_state state)
{
atomic_set(&stopmachine_thread_ack, 0);
- wmb();
+ smp_wmb();
stopmachine_state = state;
while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
cpu_relax();
diff -puN kernel/sys.c~barrier_rework_2 kernel/sys.c
--- foobar2/kernel/sys.c~barrier_rework_2 2005-03-21 12:01:06.804009291
+1100
+++ foobar2-anton/kernel/sys.c 2005-03-21 12:01:06.862004858 +1100
@@ -525,7 +525,7 @@ asmlinkage long sys_setregid(gid_t rgid,
if (new_egid != old_egid)
{
current->mm->dumpable = 0;
- wmb();
+ smp_wmb();
}
if (rgid != (gid_t) -1 ||
(egid != (gid_t) -1 && egid != old_rgid))
@@ -556,7 +556,7 @@ asmlinkage long sys_setgid(gid_t gid)
if(old_egid != gid)
{
current->mm->dumpable=0;
- wmb();
+ smp_wmb();
}
current->gid = current->egid = current->sgid = current->fsgid =
gid;
}
@@ -565,7 +565,7 @@ asmlinkage long sys_setgid(gid_t gid)
if(old_egid != gid)
{
current->mm->dumpable=0;
- wmb();
+ smp_wmb();
}
current->egid = current->fsgid = gid;
}
@@ -596,7 +596,7 @@ static int set_user(uid_t new_ruid, int
if(dumpclear)
{
current->mm->dumpable = 0;
- wmb();
+ smp_wmb();
}
current->uid = new_ruid;
return 0;
@@ -653,7 +653,7 @@ asmlinkage long sys_setreuid(uid_t ruid,
if (new_euid != old_euid)
{
current->mm->dumpable=0;
- wmb();
+ smp_wmb();
}
current->fsuid = current->euid = new_euid;
if (ruid != (uid_t) -1 ||
@@ -703,7 +703,7 @@ asmlinkage long sys_setuid(uid_t uid)
if (old_euid != uid)
{
current->mm->dumpable = 0;
- wmb();
+ smp_wmb();
}
current->fsuid = current->euid = uid;
current->suid = new_suid;
@@ -748,7 +748,7 @@ asmlinkage long sys_setresuid(uid_t ruid
if (euid != current->euid)
{
current->mm->dumpable = 0;
- wmb();
+ smp_wmb();
}
current->euid = euid;
}
@@ -798,7 +798,7 @@ asmlinkage long sys_setresgid(gid_t rgid
if (egid != current->egid)
{
current->mm->dumpable = 0;
- wmb();
+ smp_wmb();
}
current->egid = egid;
}
@@ -845,7 +845,7 @@ asmlinkage long sys_setfsuid(uid_t uid)
if (uid != old_fsuid)
{
current->mm->dumpable = 0;
- wmb();
+ smp_wmb();
}
current->fsuid = uid;
}
@@ -875,7 +875,7 @@ asmlinkage long sys_setfsgid(gid_t gid)
if (gid != old_fsgid)
{
current->mm->dumpable = 0;
- wmb();
+ smp_wmb();
}
current->fsgid = gid;
key_fsgid_changed(current);
diff -puN kernel/timer.c~barrier_rework_2 kernel/timer.c
--- foobar2/kernel/timer.c~barrier_rework_2 2005-03-21 12:01:06.809008909
+1100
+++ foobar2-anton/kernel/timer.c 2005-03-21 12:01:06.866004552 +1100
@@ -1007,7 +1007,7 @@ asmlinkage long sys_getppid(void)
* Make sure we read the pid before re-reading the
* parent pointer:
*/
- rmb();
+ smp_rmb();
parent = me->group_leader->real_parent;
if (old != parent)
continue;
diff -puN lib/rwsem-spinlock.c~barrier_rework_2 lib/rwsem-spinlock.c
--- foobar2/lib/rwsem-spinlock.c~barrier_rework_2 2005-03-21
12:01:06.814008527 +1100
+++ foobar2-anton/lib/rwsem-spinlock.c 2005-03-21 12:01:06.867004476 +1100
@@ -76,7 +76,7 @@ __rwsem_do_wake(struct rw_semaphore *sem
list_del(&waiter->list);
tsk = waiter->task;
/* Don't touch waiter after ->task has been NULLed */
- mb();
+ smp_mb();
waiter->task = NULL;
wake_up_process(tsk);
put_task_struct(tsk);
@@ -91,7 +91,7 @@ __rwsem_do_wake(struct rw_semaphore *sem
list_del(&waiter->list);
tsk = waiter->task;
- mb();
+ smp_mb();
waiter->task = NULL;
wake_up_process(tsk);
put_task_struct(tsk);
@@ -123,7 +123,7 @@ __rwsem_wake_one_writer(struct rw_semaph
list_del(&waiter->list);
tsk = waiter->task;
- mb();
+ smp_mb();
waiter->task = NULL;
wake_up_process(tsk);
put_task_struct(tsk);
diff -puN lib/rwsem.c~barrier_rework_2 lib/rwsem.c
--- foobar2/lib/rwsem.c~barrier_rework_2 2005-03-21 12:01:06.819008145
+1100
+++ foobar2-anton/lib/rwsem.c 2005-03-21 12:01:06.869004323 +1100
@@ -74,7 +74,7 @@ __rwsem_do_wake(struct rw_semaphore *sem
*/
list_del(&waiter->list);
tsk = waiter->task;
- mb();
+ smp_mb();
waiter->task = NULL;
wake_up_process(tsk);
put_task_struct(tsk);
@@ -117,7 +117,7 @@ __rwsem_do_wake(struct rw_semaphore *sem
waiter = list_entry(next, struct rwsem_waiter, list);
next = waiter->list.next;
tsk = waiter->task;
- mb();
+ smp_mb();
waiter->task = NULL;
wake_up_process(tsk);
put_task_struct(tsk);
diff -puN mm/mempool.c~barrier_rework_2 mm/mempool.c
--- foobar2/mm/mempool.c~barrier_rework_2 2005-03-21 12:01:06.824007762
+1100
+++ foobar2-anton/mm/mempool.c 2005-03-21 12:01:06.870004246 +1100
@@ -210,7 +210,7 @@ repeat_alloc:
* If the pool is less than 50% full and we can perform effective
* page reclaim then try harder to allocate an element.
*/
- mb();
+ smp_mb();
if ((gfp_mask & __GFP_FS) && (gfp_mask != gfp_nowait) &&
(pool->curr_nr <= pool->min_nr/2)) {
element = pool->alloc(gfp_mask, pool->pool_data);
@@ -236,7 +236,7 @@ repeat_alloc:
return NULL;
prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
- mb();
+ smp_mb();
if (!pool->curr_nr)
io_schedule();
finish_wait(&pool->wait, &wait);
@@ -257,7 +257,7 @@ void mempool_free(void *element, mempool
{
unsigned long flags;
- mb();
+ smp_mb();
if (pool->curr_nr < pool->min_nr) {
spin_lock_irqsave(&pool->lock, flags);
if (pool->curr_nr < pool->min_nr) {
_
