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From: Kees Cook <keescook@chromium.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Kees Cook" <keescook@chromium.org>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Juri Lelli" <juri.lelli@redhat.com>,
	"Vincent Guittot" <vincent.guittot@linaro.org>,
	"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
	"Daniel Bristot de Oliveira" <bristot@redhat.com>,
	"kernel test robot" <oliver.sang@intel.com>,
	"Vito Caputo" <vcaputo@pengaru.com>,
	"Jann Horn" <jannh@google.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Christian Brauner" <christian.brauner@ubuntu.com>,
	"Anand K Mistry" <amistry@google.com>,
	"Kenta.Tada@sony.com" <Kenta.Tada@sony.com>,
	"Alexey Gladkov" <legion@kernel.org>,
	"Michael Weiß" <michael.weiss@aisec.fraunhofer.de>,
	"Michal Hocko" <mhocko@suse.com>, "Helge Deller" <deller@gmx.de>,
	"Qi Zheng" <zhengqi.arch@bytedance.com>,
	"Tobin C. Harding" <me@tobin.cc>,
	"Tycho Andersen" <tycho@tycho.pizza>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Borislav Petkov" <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Jens Axboe" <axboe@kernel.dk>,
	"Stefan Metzmacher" <metze@samba.org>,
	"Lai Jiangshan" <laijs@linux.alibaba.com>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	"Ohhoon Kwon" <ohoono.kwon@samsung.com>,
	"Kalesh Singh" <kaleshsingh@google.com>,
	"YiFei Zhu" <yifeifz2@illinois.edu>,
	"Josh Poimboeuf" <jpoimboe@redhat.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-hardening@vger.kernel.org, x86@kernel.org
Subject: [PATCH v2 2/6] sched: Add wrapper for get_wchan() to keep task blocked
Date: Wed, 29 Sep 2021 15:02:14 -0700	[thread overview]
Message-ID: <20210929220218.691419-3-keescook@chromium.org> (raw)
In-Reply-To: <20210929220218.691419-1-keescook@chromium.org>

Having a stable wchan means the process must be blocked and for it to
stay that way while performing stack unwinding.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/sched.h |  1 +
 kernel/sched/core.c   | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 39039ce8ac4c..0c8185089e20 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2137,6 +2137,7 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
 #endif /* CONFIG_SMP */
 
 extern bool sched_task_on_rq(struct task_struct *p);
+extern unsigned long sched_task_get_wchan(struct task_struct *p);
 
 /*
  * In order to reduce various lock holder preemption latencies provide an
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1bba4128a3e6..4a30455e1ff5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1962,6 +1962,22 @@ bool sched_task_on_rq(struct task_struct *p)
 	return task_on_rq_queued(p);
 }
 
+unsigned long sched_task_get_wchan(struct task_struct *p)
+{
+	unsigned int state;
+	unsigned long ip = 0;
+
+	/* Only get wchan if task is blocked and we can keep it that way. */
+	raw_spin_lock_irq(&p->pi_lock);
+	state = READ_ONCE(p->__state);
+	smp_rmb(); /* see try_to_wake_up() */
+	if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq)
+		ip = get_wchan(p);
+	raw_spin_unlock_irq(&p->pi_lock);
+
+	return ip;
+}
+
 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
 {
 	if (!(flags & ENQUEUE_NOCLOCK))
-- 
2.30.2


  parent reply	other threads:[~2021-09-29 22:02 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-29 22:02 [PATCH v2 0/6] wchan: Fix ORC support and leaky fallback Kees Cook
2021-09-29 22:02 ` [PATCH v2 1/6] Revert "proc/wchan: use printk format instead of lookup_symbol_name()" Kees Cook
2021-09-29 22:02 ` Kees Cook [this message]
2021-09-30  8:27   ` [PATCH v2 2/6] sched: Add wrapper for get_wchan() to keep task blocked Peter Zijlstra
2021-09-30  8:28     ` Peter Zijlstra
2021-09-30  8:29       ` Peter Zijlstra
2021-09-29 22:02 ` [PATCH v2 3/6] proc: Use task_is_running() for wchan in /proc/$pid/stat Kees Cook
2021-09-29 22:02 ` [PATCH v2 4/6] proc: Only report /proc/$pid/wchan when process is blocked Kees Cook
2021-09-29 22:02 ` [PATCH v2 5/6] x86: Fix get_wchan() to support the ORC unwinder Kees Cook
2021-09-29 22:02 ` [PATCH v2 6/6] leaking_addresses: Always print a trailing newline Kees Cook
2021-09-30 14:37   ` Tycho Andersen
2021-09-30  1:01 ` [PATCH v2 0/6] wchan: Fix ORC support and leaky fallback Josh Poimboeuf
2021-09-30  8:40   ` Peter Zijlstra
2021-09-30 15:18     ` Kees Cook
2021-09-30 18:39       ` Peter Zijlstra

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