drivers/block/as-iosched.c | 73 ++++++++++++++++++++++++++++++---------------
include/linux/sched.h | 2 -
kernel/exit.c | 2 -
3 files changed, 52 insertions(+), 25 deletions(-)
diff -puN drivers/block/as-iosched.c~as-atomicity-fix drivers/block/as-iosched.c
--- 25/drivers/block/as-iosched.c~as-atomicity-fix 2003-03-05 22:17:44.000000000 -0800
+++ 25-akpm/drivers/block/as-iosched.c 2003-03-05 22:17:44.000000000 -0800
@@ -94,7 +94,7 @@ struct as_io_context {
atomic_t refcount;
pid_t pid;
unsigned long state;
- unsigned long nr_queued; /* queued reads & sync writes */
+ atomic_t nr_queued; /* queued reads & sync writes */
unsigned long nr_dispatched; /* number of requests gone to the driver */
};
@@ -186,30 +186,45 @@ static void put_as_io_context(struct as_
return;
BUG_ON(atomic_read(&aic->refcount) == 0);
+ *paic = NULL;
if (atomic_dec_and_test(&aic->refcount)) {
atomic_dec(&nr_as_io_requests);
kfree(aic);
- *paic = NULL;
}
}
/* Called by the exitting task */
-void exit_as_io_context(struct as_io_context *aic)
+void exit_as_io_context(void)
{
- clear_bit(AS_TASK_RUNNING, &aic->state);
- put_as_io_context(&aic);
+ unsigned long flags;
+ struct as_io_context *aic;
+
+ local_irq_save(flags);
+ aic = current->as_io_context;
+ if (aic) {
+ clear_bit(AS_TASK_RUNNING, &aic->state);
+ put_as_io_context(&aic);
+ current->as_io_context = NULL;
+ }
+ local_irq_restore(flags);
}
/*
- * Called from process context, by the task which is submitting I/O. If the
- * task has no IO context then create one and initialise it. If it does have
- * a context, take a ref on it.
+ * If the current task has no IO context then create one and initialise it.
+ * If it does have a context, take a ref on it.
+ *
+ * This is always called in the context of the task which submitted the I/O.
+ * But weird things happen, so we disable local interrupts to ensure exclusive
+ * access to *current.
*/
static struct as_io_context *get_as_io_context(void)
{
struct task_struct *tsk = current;
- struct as_io_context *ret = tsk->as_io_context;
+ unsigned long flags;
+ struct as_io_context *ret;
+ local_irq_save(flags);
+ ret = tsk->as_io_context;
if (ret == NULL) {
ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
if (ret) {
@@ -217,11 +232,12 @@ static struct as_io_context *get_as_io_c
atomic_set(&ret->refcount, 1);
ret->pid = tsk->pid;
ret->state = 1 << AS_TASK_RUNNING;
- ret->nr_queued = 0;
+ atomic_set(&ret->nr_queued, 0);
ret->nr_dispatched = 0;
tsk->as_io_context = ret;
}
}
+ local_irq_restore(flags);
atomic_inc(&ret->refcount);
return ret;
}
@@ -453,16 +469,21 @@ static void as_antic_waitnext(struct as_
static void as_complete_arq(struct as_data *ad, struct as_rq *arq)
{
+ if (!arq->as_io_context)
+ return;
+
set_bit(AS_REQ_FINISHED, &arq->as_io_context->state);
if (ad->as_io_context == arq->as_io_context) {
ad->antic_start = jiffies;
- if (ad->antic_status == ANTIC_WAIT_REQ)
- /* We were waiting on this request, now anticipate the
- * next one */
+ if (ad->antic_status == ANTIC_WAIT_REQ) {
+ /*
+ * We were waiting on this request, now anticipate
+ * the next one
+ */
as_antic_waitnext(ad);
+ }
}
-
put_as_io_context(&arq->as_io_context);
}
@@ -476,7 +497,8 @@ static void as_add_request(struct as_dat
const int data_dir = rq_data_dir(arq->request);
arq->as_io_context = get_as_io_context();
- arq->as_io_context->nr_queued++;
+ if (arq->as_io_context)
+ atomic_inc(&arq->as_io_context->nr_queued);
as_add_arq_rb(ad, arq);
@@ -505,8 +527,10 @@ static void as_remove_queued_request(req
const int data_dir = rq_data_dir(arq->request);
struct as_data *ad = q->elevator.elevator_data;
- BUG_ON(arq->as_io_context->nr_queued == 0);
- arq->as_io_context->nr_queued--;
+ if (arq->as_io_context) {
+ BUG_ON(!atomic_read(&arq->as_io_context->nr_queued));
+ atomic_dec(&arq->as_io_context->nr_queued);
+ }
/*
* Update the "next_arq" cache if we are about to remove its
@@ -544,9 +568,10 @@ static void as_remove_dispatched_request
if (arq) {
BUG_ON(ON_RB(&arq->rb_node));
- BUG_ON(arq->as_io_context->nr_dispatched == 0);
- arq->as_io_context->nr_dispatched--;
-
+ if (arq->as_io_context) {
+ BUG_ON(arq->as_io_context->nr_dispatched == 0);
+ arq->as_io_context->nr_dispatched--;
+ }
as_complete_arq(ad, arq);
}
}
@@ -712,7 +737,8 @@ static void as_move_to_dispatch(struct a
*/
as_remove_queued_request(ad->q, arq->request);
list_add_tail(&arq->request->queuelist, ad->dispatch);
- arq->as_io_context->nr_dispatched++;
+ if (arq->as_io_context)
+ arq->as_io_context->nr_dispatched++;
}
#define list_entry_fifo(ptr) list_entry((ptr), struct as_rq, fifo)
@@ -795,7 +821,8 @@ static void as_antic_waitreq(struct as_d
if (ad->antic_status == ANTIC_OFF) {
ant_stats.anticipate_starts++;
- if (test_bit(AS_REQ_FINISHED, &ad->as_io_context->state))
+ if (ad->as_io_context && test_bit(AS_REQ_FINISHED,
+ &ad->as_io_context->state))
as_antic_waitnext(ad);
else
ad->antic_status = ANTIC_WAIT_REQ;
@@ -912,7 +939,7 @@ static int as_can_break_anticipation(str
return 1;
}
- if (aic && aic->nr_queued > 0) {
+ if (aic && atomic_read(&aic->nr_queued) > 0) {
ant_stats.queued_request++;
return 1;
}
diff -puN kernel/exit.c~as-atomicity-fix kernel/exit.c
--- 25/kernel/exit.c~as-atomicity-fix 2003-03-05 22:17:44.000000000 -0800
+++ 25-akpm/kernel/exit.c 2003-03-05 22:17:44.000000000 -0800
@@ -695,7 +695,7 @@ NORET_TYPE void do_exit(long code)
if (unlikely(tsk->pid == 1))
panic("Attempted to kill init!");
if (tsk->as_io_context)
- exit_as_io_context(tsk->as_io_context);
+ exit_as_io_context();
tsk->flags |= PF_EXITING;
del_timer_sync(&tsk->real_timer);
diff -puN include/linux/sched.h~as-atomicity-fix include/linux/sched.h
--- 25/include/linux/sched.h~as-atomicity-fix 2003-03-05 22:17:44.000000000 -0800
+++ 25-akpm/include/linux/sched.h 2003-03-05 22:17:44.000000000 -0800
@@ -316,7 +316,7 @@ struct k_itimer {
struct as_io_context; /* Anticipatory scheduler */
-void exit_as_io_context(struct as_io_context *);
+void exit_as_io_context(void);
struct task_struct {
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
_