From: Tejun Heo <tj@kernel.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Nigel Cunningham <nigel@nigelcunningham.com.au>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Jens Axboe <axboe@kernel.dk>,
tomaz.solc@tablix.org, aaron.lu@intel.com,
linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Fengguang Wu <fengguang.wu@intel.com>,
Lai Jiangshan <laijs@cn.fujitsu.com>,
David Howells <dhowells@redhat.com>
Subject: [PATCH wq/for-3.14 1/2] workqueue: update max_active clamping rules
Date: Thu, 19 Dec 2013 18:35:26 -0500 [thread overview]
Message-ID: <20131219233526.GD22725@htj.dyndns.org> (raw)
In-Reply-To: <1735137.dNmBz0IqxU@vostro.rjw.lan>
>From bdd220b2a1b86fee14a12b69fb0cadafe60a1dac Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Thu, 19 Dec 2013 18:33:09 -0500
@max_active handling is currently inconsistent.
* In alloc_workqueue(), 0 gets converted to the default and the value
gets clamped to [1, lim].
* In workqueue_set_max_active(), 0 is not converted to the default and
the value is clamped to [1, lim].
* When a workqueue is exposed through sysfs, input < 1 fails with
-EINVAL; otherwise, the value is clamped to [1, lim].
* fscache exposes max_active through a sysctl and clamps the value in
[1, lim].
We want to be able to express zero @max_active but as it's a special
case and 0 is already used for default, don't want to use 0 for it.
Update @max_active clamping so that the following rules are followed.
* In both alloc_workqueue() and workqueue_set_max_active(), 0 is
converted to the default, and a new special value WQ_FROZEN_ACTIVE
becomes 0; otherwise, the value is clamped to [1, lim].
* In both sysfs and fscache sysctl, input < 1 fails with -EINVAL;
otherwise, the value is clamped to [1, lim].
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: David Howells <dhowells@redhat.com>
---
fs/fscache/main.c | 10 +++++++---
include/linux/workqueue.h | 1 +
kernel/workqueue.c | 6 +++++-
3 files changed, 13 insertions(+), 4 deletions(-)
diff --git a/fs/fscache/main.c b/fs/fscache/main.c
index 7c27907..9d5a716 100644
--- a/fs/fscache/main.c
+++ b/fs/fscache/main.c
@@ -62,9 +62,13 @@ static int fscache_max_active_sysctl(struct ctl_table *table, int write,
int ret;
ret = proc_dointvec(table, write, buffer, lenp, ppos);
- if (ret == 0)
- workqueue_set_max_active(*wqp, *datap);
- return ret;
+ if (ret < 0)
+ return ret;
+ if (*datap < 1)
+ return -EINVAL;
+
+ workqueue_set_max_active(*wqp, *datap);
+ return 0;
}
ctl_table fscache_sysctls[] = {
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 594521b..334daa3 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -338,6 +338,7 @@ enum {
__WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */
__WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */
+ WQ_FROZEN_ACTIVE = -1, /* special value for frozen wq */
WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */
WQ_DFL_ACTIVE = WQ_MAX_ACTIVE / 2,
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 987293d..6748fbf 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4136,6 +4136,11 @@ static int wq_clamp_max_active(int max_active, unsigned int flags,
{
int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
+ if (max_active == 0)
+ return WQ_DFL_ACTIVE;
+ if (max_active == WQ_FROZEN_ACTIVE)
+ return 0;
+
if (max_active < 1 || max_active > lim)
pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
max_active, name, 1, lim);
@@ -4176,7 +4181,6 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
vsnprintf(wq->name, sizeof(wq->name), fmt, args);
va_end(args);
- max_active = max_active ?: WQ_DFL_ACTIVE;
max_active = wq_clamp_max_active(max_active, flags, wq->name);
/* init wq */
--
1.8.4.2
next prev parent reply other threads:[~2013-12-19 23:35 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-13 17:49 Writeback threads and freezable Tejun Heo
2013-12-13 18:52 ` Tejun Heo
2013-12-13 20:40 ` [PATCH] libata, freezer: avoid block device removal while system is frozen Tejun Heo
2013-12-13 22:45 ` Nigel Cunningham
2013-12-13 23:07 ` Tejun Heo
2013-12-13 23:15 ` Nigel Cunningham
2013-12-14 1:55 ` Dave Chinner
2013-12-14 20:31 ` Tejun Heo
2013-12-14 20:36 ` Tejun Heo
2013-12-14 21:21 ` Nigel Cunningham
2013-12-17 2:35 ` Rafael J. Wysocki
2013-12-17 2:34 ` Rafael J. Wysocki
2013-12-17 12:34 ` Tejun Heo
2013-12-18 0:35 ` Rafael J. Wysocki
2013-12-18 11:17 ` Tejun Heo
2013-12-18 21:48 ` Rafael J. Wysocki
2013-12-18 21:39 ` Tejun Heo
2013-12-18 21:41 ` Tejun Heo
2013-12-18 22:04 ` Rafael J. Wysocki
2013-12-19 23:35 ` Tejun Heo [this message]
2013-12-20 1:26 ` [PATCH wq/for-3.14 1/2] workqueue: update max_active clamping rules Rafael J. Wysocki
2013-12-19 23:37 ` [PATCH wq/for-3.14 2/2] workqueue: implement @drain for workqueue_set_max_active() Tejun Heo
2013-12-20 1:31 ` Rafael J. Wysocki
2013-12-20 13:32 ` Tejun Heo
2013-12-20 13:56 ` Rafael J. Wysocki
2013-12-20 14:23 ` Tejun Heo
2013-12-16 12:12 ` [PATCH] libata, freezer: avoid block device removal while system is frozen Ming Lei
2013-12-16 12:45 ` Tejun Heo
2013-12-16 13:24 ` Ming Lei
2013-12-16 16:05 ` Tejun Heo
2013-12-17 2:38 ` Rafael J. Wysocki
2013-12-17 12:36 ` Tejun Heo
2013-12-18 0:23 ` Rafael J. Wysocki
2013-12-17 12:50 ` [PATCH v2] " Tejun Heo
2013-12-18 1:04 ` Rafael J. Wysocki
2013-12-18 11:08 ` Tejun Heo
2013-12-18 12:07 ` [PATCH v3] " Tejun Heo
2013-12-18 22:08 ` Rafael J. Wysocki
2013-12-19 17:24 ` Tejun Heo
2013-12-19 18:54 ` [PATCH v4] " Tejun Heo
2013-12-14 1:53 ` Writeback threads and freezable Dave Chinner
2013-12-14 17:30 ` Greg Kroah-Hartman
2013-12-14 20:23 ` Tejun Heo
2013-12-16 3:56 ` Dave Chinner
2013-12-16 12:51 ` Tejun Heo
2013-12-16 12:56 ` Tejun Heo
2013-12-18 0:35 ` Dave Chinner
2013-12-18 11:43 ` Tejun Heo
2013-12-18 22:14 ` Rafael J. Wysocki
2013-12-19 4:08 ` Dave Chinner
2013-12-19 16:24 ` Tejun Heo
2013-12-20 0:51 ` Dave Chinner
2013-12-20 14:51 ` Tejun Heo
2013-12-20 14:00 ` Rafael J. Wysocki
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