lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <1429728220.10273.26.camel@stgolabs.net>
Date:	Wed, 22 Apr 2015 11:43:40 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	Mike Miller <mike.miller@...com>, Don Brace <don.brace@...s.com>,
	iss_storagedev@...com, storagedev@...s.com,
	linux-kernel@...r.kernel.org, dave@...olabs.net
Subject: [PATCH] cciss: Optimize scan_thread

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@...e.de>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Mike Miller <mike.miller@...com>
Cc: Don Brace <don.brace@...s.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



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ