From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Will Deacon <will@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E . McKenney" <paulmck@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Evgeniy Polyakov <zbr@ioremap.net>,
netdev@vger.kernel.org,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH v3 5/7] connector/cn_proc: Protect send_msg() with a local lock
Date: Wed, 27 May 2020 22:11:17 +0200 [thread overview]
Message-ID: <20200527201119.1692513-6-bigeasy@linutronix.de> (raw)
In-Reply-To: <20200527201119.1692513-1-bigeasy@linutronix.de>
From: Mike Galbraith <umgwanakikbuti@gmail.com>
send_msg() disables preemption to avoid out-of-order messages. As the
code inside the preempt disabled section acquires regular spinlocks,
which are converted to 'sleeping' spinlocks on a PREEMPT_RT kernel and
eventually calls into a memory allocator, this conflicts with the RT
semantics.
Convert it to a local_lock which allows RT kernels to substitute them with
a real per CPU lock. On non RT kernels this maps to preempt_disable() as
before. No functional change.
[bigeasy: Patch description]
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/connector/cn_proc.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)
diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
index d58ce664da843..646ad385e4904 100644
--- a/drivers/connector/cn_proc.c
+++ b/drivers/connector/cn_proc.c
@@ -18,6 +18,7 @@
#include <linux/pid_namespace.h>
#include <linux/cn_proc.h>
+#include <linux/local_lock.h>
/*
* Size of a cn_msg followed by a proc_event structure. Since the
@@ -38,25 +39,31 @@ static inline struct cn_msg *buffer_to_cn_msg(__u8 *buffer)
static atomic_t proc_event_num_listeners = ATOMIC_INIT(0);
static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC };
-/* proc_event_counts is used as the sequence number of the netlink message */
-static DEFINE_PER_CPU(__u32, proc_event_counts) = { 0 };
+/* local_event.count is used as the sequence number of the netlink message */
+struct local_event {
+ local_lock_t lock;
+ __u32 count;
+};
+static DEFINE_PER_CPU(struct local_event, local_event) = {
+ .lock = INIT_LOCAL_LOCK(lock),
+};
static inline void send_msg(struct cn_msg *msg)
{
- preempt_disable();
+ local_lock(&local_event.lock);
- msg->seq = __this_cpu_inc_return(proc_event_counts) - 1;
+ msg->seq = __this_cpu_inc_return(local_event.count) - 1;
((struct proc_event *)msg->data)->cpu = smp_processor_id();
/*
- * Preemption remains disabled during send to ensure the messages are
- * ordered according to their sequence numbers.
+ * local_lock() disables preemption during send to ensure the messages
+ * are ordered according to their sequence numbers.
*
* If cn_netlink_send() fails, the data is not sent.
*/
cn_netlink_send(msg, 0, CN_IDX_PROC, GFP_NOWAIT);
- preempt_enable();
+ local_unlock(&local_event.lock);
}
void proc_fork_connector(struct task_struct *task)
--
2.27.0.rc0
next prev parent reply other threads:[~2020-05-27 20:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 20:11 [PATCH v3 0/7] Introduce local_lock() Sebastian Andrzej Siewior
2020-05-27 20:11 ` [PATCH v3 1/7] locking: " Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Thomas Gleixner
2020-05-27 20:11 ` [PATCH v3 2/7] radix-tree: Use local_lock for protection Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Sebastian Andrzej Siewior
2020-05-27 20:11 ` [PATCH v3 3/7] mm/swap: " Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Ingo Molnar
2020-05-27 20:11 ` [PATCH v3 4/7] squashfs: make use of local lock in multi_cpu decompressor Sebastian Andrzej Siewior
2020-06-01 9:52 ` [tip: locking/core] squashfs: Make " tip-bot2 for Julia Cartwright
2020-05-27 20:11 ` Sebastian Andrzej Siewior [this message]
2020-06-01 9:52 ` [tip: locking/core] connector/cn_proc: Protect send_msg() with a local lock tip-bot2 for Mike Galbraith
2020-05-27 20:11 ` [PATCH v3 6/7] zram: Allocate struct zcomp_strm as per-CPU memory Sebastian Andrzej Siewior
2020-05-29 20:51 ` Minchan Kim
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Sebastian Andrzej Siewior
2020-05-27 20:11 ` [PATCH v3 7/7] zram: Use local lock to protect per-CPU data Sebastian Andrzej Siewior
2020-05-29 20:57 ` Minchan Kim
2020-06-01 9:52 ` [tip: locking/core] " tip-bot2 for Mike Galbraith
2020-10-19 1:52 ` [PATCH v3 7/7] " Yu Zhao
2020-10-19 2:33 ` Hugh Dickins
2020-10-19 2:46 ` Mike Galbraith
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=20200527201119.1692513-6-bigeasy@linutronix.de \
--to=bigeasy@linutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=umgwanakikbuti@gmail.com \
--cc=will@kernel.org \
--cc=willy@infradead.org \
--cc=zbr@ioremap.net \
/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).