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Date: Wed, 29 Sep 2021 15:02:14 -0700 From: Kees Cook <keescook@...omium.org> To: Peter Zijlstra <peterz@...radead.org> Cc: Kees Cook <keescook@...omium.org>, Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>, kernel test robot <oliver.sang@...el.com>, Vito Caputo <vcaputo@...garu.com>, Jann Horn <jannh@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Christian Brauner <christian.brauner@...ntu.com>, Anand K Mistry <amistry@...gle.com>, "Kenta.Tada@...y.com" <Kenta.Tada@...y.com>, Alexey Gladkov <legion@...nel.org>, Michael Weiß <michael.weiss@...ec.fraunhofer.de>, Michal Hocko <mhocko@...e.com>, Helge Deller <deller@....de>, Qi Zheng <zhengqi.arch@...edance.com>, "Tobin C. Harding" <me@...in.cc>, Tycho Andersen <tycho@...ho.pizza>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Mark Rutland <mark.rutland@....com>, Jens Axboe <axboe@...nel.dk>, Stefan Metzmacher <metze@...ba.org>, Lai Jiangshan <laijs@...ux.alibaba.com>, Andy Lutomirski <luto@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, Ohhoon Kwon <ohoono.kwon@...sung.com>, Kalesh Singh <kaleshsingh@...gle.com>, YiFei Zhu <yifeifz2@...inois.edu>, Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-hardening@...r.kernel.org, x86@...nel.org Subject: [PATCH v2 2/6] sched: Add wrapper for get_wchan() to keep task blocked 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@...hat.com> Cc: Juri Lelli <juri.lelli@...hat.com> Cc: Vincent Guittot <vincent.guittot@...aro.org> Cc: Dietmar Eggemann <dietmar.eggemann@....com> Cc: Steven Rostedt <rostedt@...dmis.org> Cc: Ben Segall <bsegall@...gle.com> Cc: Mel Gorman <mgorman@...e.de> Cc: Daniel Bristot de Oliveira <bristot@...hat.com> Suggested-by: Peter Zijlstra <peterz@...radead.org> Signed-off-by: Kees Cook <keescook@...omium.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
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