Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 11 Nov 2014 11:39:49 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/5] sched_show_task: fix unsafe usage of ->real_parent |
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On Mon, Nov 10, 2014 at 11:00:26PM +0100, Oleg Nesterov wrote: > rcu_read_lock() can not protect p->real_parent if release_task(p) was > already called, change sched_show_task() to check pis_alive() like > other users do. > > Note: we need some helpers to cleanup the code like this. And it seems > that that the usage of cpu_curr(cpu) in dump_cpu_task() is not safe too. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> --- > kernel/sched/core.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 240157c..1ec75c9 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -4572,8 +4572,10 @@ void sched_show_task(struct task_struct *p) > #ifdef CONFIG_DEBUG_STACK_USAGE > free = stack_not_used(p); > #endif > + ppid = 0; > rcu_read_lock(); > - ppid = task_pid_nr(rcu_dereference(p->real_parent)); > + if (pid_alive(p)) > + ppid = task_pid_nr(rcu_dereference(p->real_parent)); > rcu_read_unlock(); > printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free, > task_pid_nr(p), ppid, > -- > 1.5.5.1 >
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