From: "tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: stable@kernel.org,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Valentin Schneider <valentin.schneider@arm.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/urgent] sched: Simplify set_affinity_pending refcounts
Date: Mon, 01 Mar 2021 10:16:16 -0000 [thread overview]
Message-ID: <161459377628.20312.17557474951313290119.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210224131355.724130207@infradead.org>
The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: a4c2579076dc6951709a8e425df8369ab6eb2f24
Gitweb: https://git.kernel.org/tip/a4c2579076dc6951709a8e425df8369ab6eb2f24
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 24 Feb 2021 11:42:08 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 01 Mar 2021 11:02:15 +01:00
sched: Simplify set_affinity_pending refcounts
Now that we have set_affinity_pending::stop_pending to indicate if a
stopper is in progress, and we have the guarantee that if that stopper
exists, it will (eventually) complete our @pending we can simplify the
refcount scheme by no longer counting the stopper thread.
Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.724130207@infradead.org
---
kernel/sched/core.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4e4d100..9819121 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1862,6 +1862,10 @@ struct migration_arg {
struct set_affinity_pending *pending;
};
+/*
+ * @refs: number of wait_for_completion()
+ * @stop_pending: is @stop_work in use
+ */
struct set_affinity_pending {
refcount_t refs;
unsigned int stop_pending;
@@ -1997,10 +2001,6 @@ out:
if (complete)
complete_all(&pending->done);
- /* For pending->{arg,stop_work} */
- if (pending && refcount_dec_and_test(&pending->refs))
- wake_up_var(&pending->refs);
-
return 0;
}
@@ -2199,12 +2199,16 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
push_task = get_task_struct(p);
}
+ /*
+ * If there are pending waiters, but no pending stop_work,
+ * then complete now.
+ */
pending = p->migration_pending;
- if (pending) {
- refcount_inc(&pending->refs);
+ if (pending && !pending->stop_pending) {
p->migration_pending = NULL;
complete = true;
}
+
task_rq_unlock(rq, p, rf);
if (push_task) {
@@ -2213,7 +2217,7 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
}
if (complete)
- goto do_complete;
+ complete_all(&pending->done);
return 0;
}
@@ -2264,9 +2268,9 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
if (!stop_pending)
pending->stop_pending = true;
- refcount_inc(&pending->refs); /* pending->{arg,stop_work} */
if (flags & SCA_MIGRATE_ENABLE)
p->migration_flags &= ~MDF_PUSH;
+
task_rq_unlock(rq, p, rf);
if (!stop_pending) {
@@ -2282,12 +2286,13 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
if (task_on_rq_queued(p))
rq = move_queued_task(rq, rf, p, dest_cpu);
- p->migration_pending = NULL;
- complete = true;
+ if (!pending->stop_pending) {
+ p->migration_pending = NULL;
+ complete = true;
+ }
}
task_rq_unlock(rq, p, rf);
-do_complete:
if (complete)
complete_all(&pending->done);
}
@@ -2295,7 +2300,7 @@ do_complete:
wait_for_completion(&pending->done);
if (refcount_dec_and_test(&pending->refs))
- wake_up_var(&pending->refs);
+ wake_up_var(&pending->refs); /* No UaF, just an address */
/*
* Block the original owner of &pending until all subsequent callers
@@ -2303,6 +2308,9 @@ do_complete:
*/
wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs));
+ /* ARGH */
+ WARN_ON_ONCE(my_pending.stop_pending);
+
return 0;
}
next prev parent reply other threads:[~2021-03-01 10:18 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-24 12:24 [PATCH 0/6] sched: Fix affine_move_task() wreckage Peter Zijlstra
2021-02-24 12:24 ` [PATCH 1/6] sched: Fix migration_cpu_stop() requeueing Peter Zijlstra
2021-03-01 10:16 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-03-06 11:42 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-02-24 12:24 ` [PATCH 2/6] sched: Simplify migration_cpu_stop() Peter Zijlstra
2021-02-24 15:34 ` Valentin Schneider
2021-02-25 8:45 ` Peter Zijlstra
2021-02-25 11:10 ` Valentin Schneider
2021-03-01 10:16 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-03-06 11:42 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-02-24 12:24 ` [PATCH 3/6] sched: Collate affine_move_task() stoppers Peter Zijlstra
2021-03-01 10:16 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-03-06 11:42 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-02-24 12:24 ` [PATCH 4/6] sched: Optimize migration_cpu_stop() Peter Zijlstra
2021-03-01 10:16 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-03-06 11:42 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-02-24 12:24 ` [PATCH 5/6] sched: Fix affine_move_task() self-concurrency Peter Zijlstra
2021-03-01 10:16 ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2021-03-06 11:42 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-02-24 12:24 ` [PATCH 6/6] sched: Simplify set_affinity_pending refcounts Peter Zijlstra
2021-02-24 15:34 ` Valentin Schneider
2021-02-24 15:34 ` Peter Zijlstra
2021-02-24 17:59 ` Valentin Schneider
2021-02-25 9:27 ` Peter Zijlstra
2021-02-25 11:11 ` Valentin Schneider
2021-03-01 10:16 ` tip-bot2 for Peter Zijlstra [this message]
2021-03-06 11:42 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
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=161459377628.20312.17557474951313290119.tip-bot2@tip-bot2 \
--to=tip-bot2@linutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=peterz@infradead.org \
--cc=stable@kernel.org \
--cc=valentin.schneider@arm.com \
--cc=x86@kernel.org \
/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).