From: Frederic Weisbecker <frederic@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Oleg Nesterov <oleg@redhat.com>
Subject: [PATCH 1/6] posix-cpu-timers: Assert task sighand is locked while starting cputime counter
Date: Mon, 26 Jul 2021 14:55:08 +0200 [thread overview]
Message-ID: <20210726125513.271824-2-frederic@kernel.org> (raw)
In-Reply-To: <20210726125513.271824-1-frederic@kernel.org>
Starting the process wide cputime counter needs to be done in the same
sighand locking sequence than actually arming the related timer
otherwise we risk races against concurrent timers setting/expiring
in the same threadgroup.
Detecting that we start the cputime counter without holding the sighand
lock is a first step toward debugging such situations.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
---
include/linux/sched/signal.h | 6 ++++++
kernel/signal.c | 15 +++++++++++++++
kernel/time/posix-cpu-timers.c | 2 ++
3 files changed, 23 insertions(+)
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index b9126fe06c3f..0310a5add9ab 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -714,6 +714,12 @@ static inline void unlock_task_sighand(struct task_struct *task,
spin_unlock_irqrestore(&task->sighand->siglock, *flags);
}
+#ifdef CONFIG_LOCKDEP
+extern void lockdep_assert_task_sighand_held(struct task_struct *task);
+#else
+static inline void lockdep_assert_task_sighand_held(struct task_struct *task) { }
+#endif
+
static inline unsigned long task_rlimit(const struct task_struct *task,
unsigned int limit)
{
diff --git a/kernel/signal.c b/kernel/signal.c
index a3229add4455..52b6abec0ff8 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1413,6 +1413,21 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
return sighand;
}
+#ifdef CONFIG_LOCKDEP
+void lockdep_assert_task_sighand_held(struct task_struct *task)
+{
+ struct sighand_struct *sighand;
+
+ rcu_read_lock();
+ sighand = rcu_dereference(task->sighand);
+ if (sighand)
+ lockdep_assert_held(&sighand->siglock);
+ else
+ WARN_ON_ONCE(1);
+ rcu_read_unlock();
+}
+#endif
+
/*
* send signal info to all the members of a group
*/
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 517be7fd175e..4693d3c71e7e 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -291,6 +291,8 @@ static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
+ lockdep_assert_task_sighand_held(tsk);
+
/* Check if cputimer isn't running. This is accessed without locking. */
if (!READ_ONCE(pct->timers_active)) {
struct task_cputime sum;
--
2.25.1
next prev parent reply other threads:[~2021-07-26 12:55 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-26 12:55 [GIT PULL] posix-cpu-timers leftover overhead fixes Frederic Weisbecker
2021-07-26 12:55 ` Frederic Weisbecker [this message]
2021-08-10 15:13 ` [tip: timers/core] posix-cpu-timers: Assert task sighand is locked while starting cputime counter tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 2/6] posix-cpu-timers: Force next_expiration recalc after timer deletion Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 3/6] posix-cpu-timers: Force next expiration recalc after itimer reset Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 4/6] posix-cpu-timers: Remove confusing error code override Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] posix-cpu-timers: Remove confusing return value override tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 5/6] posix-cpu-timers: Consolidate timer base accessor Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 6/6] posix-cpu-timers: Recalc next expiration when timer_settime() ends up not queueing Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
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=20210726125513.271824-2-frederic@kernel.org \
--to=frederic@kernel.org \
--cc=ebiederm@xmission.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
/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).