target: stop task timers earlier
Christoph Hellwig [Mon, 17 Oct 2011 17:56:48 +0000 (13:56 -0400)]
Currently we stop the timers for all tasks in a command fairly late during
I/O completion, which is fairly pointless and requires all kinds of safety
checks.

Instead delete pending timers early on in transport_complete_task, thus
ensuring no new timers firest after that.  We take t_state_lock a bit later
in that function thus making sure currenly running timers are out of the
criticial section.  To be completely sure the timer has finished we also
add another del_timer_sync call when freeing the task.

This also allows removing TF_TIMER_RUNNING as it would be equivalent
to TF_ACTIVE now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_transport.c
include/target/target_core_base.h
include/target/target_core_transport.h

index a36f445..19ea1c3 100644 (file)
@@ -84,7 +84,6 @@ static int transport_generic_get_mem(struct se_cmd *cmd);
 static void transport_put_cmd(struct se_cmd *cmd);
 static void transport_remove_cmd_from_queue(struct se_cmd *cmd);
 static int transport_set_sense_codes(struct se_cmd *cmd, u8 asc, u8 ascq);
-static void transport_stop_all_task_timers(struct se_cmd *cmd);
 
 int init_se_kmem_caches(void)
 {
@@ -712,6 +711,8 @@ void transport_complete_task(struct se_task *task, int success)
        if (dev)
                atomic_inc(&dev->depth_left);
 
+       del_timer(&task->task_timer);
+
        spin_lock_irqsave(&cmd->t_state_lock, flags);
        task->task_flags &= ~TF_ACTIVE;
 
@@ -1507,6 +1508,7 @@ transport_generic_get_task(struct se_cmd *cmd,
        INIT_LIST_HEAD(&task->t_list);
        INIT_LIST_HEAD(&task->t_execute_list);
        INIT_LIST_HEAD(&task->t_state_list);
+       init_timer(&task->task_timer);
        init_completion(&task->task_stop_comp);
        task->task_se_cmd = cmd;
        task->task_data_direction = data_direction;
@@ -1776,6 +1778,7 @@ bool target_stop_task(struct se_task *task, unsigned long *flags)
                spin_unlock_irqrestore(&cmd->t_state_lock, *flags);
 
                pr_debug("Task %p waiting to complete\n", task);
+               del_timer_sync(&task->task_timer);
                wait_for_completion(&task->task_stop_comp);
                pr_debug("Task %p stopped successfully\n", task);
 
@@ -1785,7 +1788,6 @@ bool target_stop_task(struct se_task *task, unsigned long *flags)
                was_active = true;
        }
 
-       __transport_stop_task_timer(task, flags);
        return was_active;
 }
 
@@ -1860,8 +1862,6 @@ static void transport_generic_request_failure(
                atomic_read(&cmd->t_transport_stop),
                atomic_read(&cmd->t_transport_sent));
 
-       transport_stop_all_task_timers(cmd);
-
        if (dev)
                atomic_inc(&dev->depth_left);
        /*
@@ -2066,7 +2066,6 @@ static void transport_task_timeout_handler(unsigned long data)
        pr_debug("transport task timeout fired! task: %p cmd: %p\n", task, cmd);
 
        spin_lock_irqsave(&cmd->t_state_lock, flags);
-       task->task_flags &= ~TF_TIMER_RUNNING;
 
        /*
         * Determine if transport_complete_task() has already been called.
@@ -2109,16 +2108,11 @@ static void transport_task_timeout_handler(unsigned long data)
        transport_add_cmd_to_queue(cmd, TRANSPORT_COMPLETE_FAILURE, false);
 }
 
-/*
- * Called with cmd->t_state_lock held.
- */
 static void transport_start_task_timer(struct se_task *task)
 {
        struct se_device *dev = task->task_se_cmd->se_dev;
        int timeout;
 
-       if (task->task_flags & TF_TIMER_RUNNING)
-               return;
        /*
         * If the task_timeout is disabled, exit now.
         */
@@ -2126,47 +2120,10 @@ static void transport_start_task_timer(struct se_task *task)
        if (!timeout)
                return;
 
-       init_timer(&task->task_timer);
        task->task_timer.expires = (get_jiffies_64() + timeout * HZ);
        task->task_timer.data = (unsigned long) task;
        task->task_timer.function = transport_task_timeout_handler;
-
-       task->task_flags |= TF_TIMER_RUNNING;
        add_timer(&task->task_timer);
-#if 0
-       pr_debug("Starting task timer for cmd: %p task: %p seconds:"
-               " %d\n", task->task_se_cmd, task, timeout);
-#endif
-}
-
-/*
- * Called with spin_lock_irq(&cmd->t_state_lock) held.
- */
-void __transport_stop_task_timer(struct se_task *task, unsigned long *flags)
-{
-       struct se_cmd *cmd = task->task_se_cmd;
-
-       if (!(task->task_flags & TF_TIMER_RUNNING))
-               return;
-
-       spin_unlock_irqrestore(&cmd->t_state_lock, *flags);
-
-       del_timer_sync(&task->task_timer);
-
-       spin_lock_irqsave(&cmd->t_state_lock, *flags);
-       task->task_flags &= ~TF_TIMER_RUNNING;
-}
-
-static void transport_stop_all_task_timers(struct se_cmd *cmd)
-{
-       struct se_task *task = NULL, *task_tmp;
-       unsigned long flags;
-
-       spin_lock_irqsave(&cmd->t_state_lock, flags);
-       list_for_each_entry_safe(task, task_tmp,
-                               &cmd->t_task_list, t_list)
-               __transport_stop_task_timer(task, &flags);
-       spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 }
 
 static inline int transport_tcq_window_closed(struct se_device *dev)
@@ -2365,6 +2322,7 @@ check_depth:
                        spin_lock_irqsave(&cmd->t_state_lock, flags);
                        task->task_flags &= ~TF_ACTIVE;
                        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+                       del_timer_sync(&task->task_timer);
                        atomic_set(&cmd->transport_sent, 0);
                        transport_stop_tasks_for_cmd(cmd);
                        transport_generic_request_failure(cmd, dev, 0, 1);
@@ -2403,6 +2361,7 @@ check_depth:
                        spin_lock_irqsave(&cmd->t_state_lock, flags);
                        task->task_flags &= ~TF_ACTIVE;
                        spin_unlock_irqrestore(&cmd->t_state_lock, flags);
+                       del_timer_sync(&task->task_timer);
                        atomic_set(&cmd->transport_sent, 0);
                        transport_stop_tasks_for_cmd(cmd);
                        transport_generic_request_failure(cmd, dev, 0, 1);
@@ -3431,7 +3390,6 @@ static void transport_complete_qf(struct se_cmd *cmd)
 {
        int ret = 0;
 
-       transport_stop_all_task_timers(cmd);
        if (cmd->se_dev->dev_task_attr_type == SAM_TASK_ATTR_EMULATED)
                transport_complete_task_attr(cmd);
 
@@ -3601,6 +3559,14 @@ static void transport_free_dev_tasks(struct se_cmd *cmd)
        while (!list_empty(&dispose_list)) {
                task = list_first_entry(&dispose_list, struct se_task, t_list);
 
+               /*
+                * We already cancelled all pending timers in
+                * transport_complete_task, but that was just a pure del_timer,
+                * so do a full del_timer_sync here to make sure any handler
+                * that was running at that point has finished execution.
+                */
+               del_timer_sync(&task->task_timer);
+
                kfree(task->task_sg_bidi);
                kfree(task->task_sg);
 
@@ -4820,7 +4786,6 @@ get_cmd:
                        transport_generic_process_write(cmd);
                        break;
                case TRANSPORT_COMPLETE_OK:
-                       transport_stop_all_task_timers(cmd);
                        transport_generic_complete_ok(cmd);
                        break;
                case TRANSPORT_REMOVE:
@@ -4836,7 +4801,6 @@ get_cmd:
                        transport_generic_request_failure(cmd, NULL, 1, 1);
                        break;
                case TRANSPORT_COMPLETE_TIMEOUT:
-                       transport_stop_all_task_timers(cmd);
                        transport_generic_request_timeout(cmd);
                        break;
                case TRANSPORT_COMPLETE_QF_WP:
index 8f02a65..0271936 100644 (file)
@@ -77,7 +77,6 @@ enum se_task_flags {
        TF_SENT                 = (1 << 1),
        TF_TIMEOUT              = (1 << 2),
        TF_REQUEST_STOP         = (1 << 3),
-       TF_TIMER_RUNNING        = (1 << 4),
 };
 
 /* Special transport agnostic struct se_cmd->t_states */
index 1ba5835..c8538c5 100644 (file)
@@ -172,7 +172,6 @@ extern void transport_new_cmd_failure(struct se_cmd *);
 extern int transport_generic_handle_tmr(struct se_cmd *);
 extern void transport_generic_free_cmd_intr(struct se_cmd *);
 extern bool target_stop_task(struct se_task *task, unsigned long *flags);
-extern void __transport_stop_task_timer(struct se_task *, unsigned long *);
 extern int transport_generic_map_mem_to_cmd(struct se_cmd *cmd, struct scatterlist *, u32,
                                struct scatterlist *, u32);
 extern int transport_clear_lun_from_sessions(struct se_lun *);