Messages in this thread Patch in this message | | | Subject | [PATCH] cciss: Optimize scan_thread | From | Davidlohr Bueso <> | Date | Wed, 22 Apr 2015 11:43:40 -0700 |
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Two rather small optimizations found while going through driver code:
1) Use the cheaper alternative to set_current_state() as we are sure the task will block right afterward.
2) Checks for list_empty without the scan_mutex. The list_empty function is very much designed to work without locks, obviously as long as the head (scan_q) is reliable. In this case if another thread is doing add_to_scan_list(), we still buckle in the outer loop, so it will be caught upon the next iteration -- and if kthread_should_stop() hits, it does not matter _anyway_ as we'd still need to abort the function regardless of the status of the scan_q.
Compile tested only.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Cc: Jens Axboe <axboe@kernel.dk> Cc: Mike Miller <mike.miller@hp.com> Cc: Don Brace <don.brace@pmcs.com> --- drivers/block/cciss.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c index ff20f19..7dd3750 100644 --- a/drivers/block/cciss.c +++ b/drivers/block/cciss.c @@ -3727,18 +3727,13 @@ static int scan_thread(void *data) struct ctlr_info *h; while (1) { - set_current_state(TASK_INTERRUPTIBLE); + __set_current_state(TASK_INTERRUPTIBLE); schedule(); if (kthread_should_stop()) break; - while (1) { + while (!list_empty(&scan_q)) { mutex_lock(&scan_mutex); - if (list_empty(&scan_q)) { - mutex_unlock(&scan_mutex); - break; - } - h = list_entry(scan_q.next, struct ctlr_info, scan_list); -- 2.1.4
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