From: Douglas Gilbert <dgilbert@interlog.com>
To: linux-scsi@vger.kernel.org
Cc: martin.petersen@oracle.com, jejb@linux.vnet.ibm.com,
hare@suse.de, bvanassche@acm.org
Subject: [PATCH v2 4/9] scsi_debug: refine sdebug_blk_mq_poll
Date: Sat, 8 Jan 2022 20:28:48 -0500 [thread overview]
Message-ID: <20220109012853.301953-5-dgilbert@interlog.com> (raw)
In-Reply-To: <20220109012853.301953-1-dgilbert@interlog.com>
Refine the sdebug_blk_mq_poll() function so it only takes the
spinlock on the queue when it can see one or more requests
with the in_use bitmap flag set.
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
---
drivers/scsi/scsi_debug.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 8abe95a0d869..c6798d991fbe 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -7396,6 +7396,7 @@ static int sdebug_blk_mq_poll(struct Scsi_Host *shost, unsigned int queue_num)
{
bool first;
bool retiring = false;
+ bool locked = false;
int num_entries = 0;
unsigned int qc_idx = 0;
unsigned long iflags;
@@ -7407,16 +7408,23 @@ static int sdebug_blk_mq_poll(struct Scsi_Host *shost, unsigned int queue_num)
struct sdebug_defer *sd_dp;
sqp = sdebug_q_arr + queue_num;
- spin_lock_irqsave(&sqp->qc_lock, iflags);
+ qc_idx = find_first_bit(sqp->in_use_bm, sdebug_max_queue);
+ if (qc_idx >= sdebug_max_queue)
+ return 0;
for (first = true; first || qc_idx + 1 < sdebug_max_queue; ) {
+ if (!locked) {
+ spin_lock_irqsave(&sqp->qc_lock, iflags);
+ locked = true;
+ }
if (first) {
- qc_idx = find_first_bit(sqp->in_use_bm, sdebug_max_queue);
first = false;
+ if (!test_bit(qc_idx, sqp->in_use_bm))
+ continue;
} else {
qc_idx = find_next_bit(sqp->in_use_bm, sdebug_max_queue, qc_idx + 1);
}
- if (unlikely(qc_idx >= sdebug_max_queue))
+ if (qc_idx >= sdebug_max_queue)
break;
sqcp = &sqp->qc_arr[qc_idx];
@@ -7465,11 +7473,14 @@ static int sdebug_blk_mq_poll(struct Scsi_Host *shost, unsigned int queue_num)
}
WRITE_ONCE(sd_dp->defer_t, SDEB_DEFER_NONE);
spin_unlock_irqrestore(&sqp->qc_lock, iflags);
+ locked = false;
scsi_done(scp); /* callback to mid level */
- spin_lock_irqsave(&sqp->qc_lock, iflags);
num_entries++;
+ if (find_first_bit(sqp->in_use_bm, sdebug_max_queue) >= sdebug_max_queue)
+ break; /* if no more then exit without retaking spinlock */
}
- spin_unlock_irqrestore(&sqp->qc_lock, iflags);
+ if (locked)
+ spin_unlock_irqrestore(&sqp->qc_lock, iflags);
if (num_entries > 0)
atomic_add(num_entries, &sdeb_mq_poll_count);
return num_entries;
--
2.25.1
next prev parent reply other threads:[~2022-01-09 1:29 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-09 1:28 [PATCH v2 0/9] scsi_debug: collection of additions Douglas Gilbert
2022-01-09 1:28 ` [PATCH v2 1/9] scsi_debug: address races following module load Douglas Gilbert
2022-01-09 1:28 ` [PATCH v2 2/9] scsi_debug: strengthen defer_t accesses Douglas Gilbert
2022-01-09 1:28 ` [PATCH v2 3/9] scsi_debug: use task set full more Douglas Gilbert
2022-01-09 1:28 ` Douglas Gilbert [this message]
2022-01-09 1:28 ` [PATCH v2 5/9] scsi_debug: divide power on reset unit attention Douglas Gilbert
2022-01-09 1:28 ` [PATCH v2 6/9] scsi_debug: add no_rwlock parameter Douglas Gilbert
2022-01-09 1:28 ` [PATCH v2 7/9] scsi_debug: add sdeb_sgl_copy_sgl and friends Douglas Gilbert
2022-01-09 1:28 ` [PATCH v2 8/9] scsi_debug: change store from vmalloc to sgl Douglas Gilbert
2022-01-09 1:28 ` [PATCH v2 9/9] scsi_debug: add environmental reporting log subpage Douglas Gilbert
2022-01-25 5:38 ` [PATCH v2 0/9] scsi_debug: collection of additions Martin K. Petersen
2022-02-01 2:04 ` Martin K. Petersen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220109012853.301953-5-dgilbert@interlog.com \
--to=dgilbert@interlog.com \
--cc=bvanassche@acm.org \
--cc=hare@suse.de \
--cc=jejb@linux.vnet.ibm.com \
--cc=linux-scsi@vger.kernel.org \
--cc=martin.petersen@oracle.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).