Messages in this thread | | | Date | Wed, 24 Oct 2012 22:50:56 -0700 | From | Sergey Senozhatsky <> | Subject | Re: lots of suspicious RCU traces |
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On (10/25/12 00:32), Frederic Weisbecker wrote: > First of all, thanks a lot for your report. > > 2012/10/24 Sergey Senozhatsky <sergey.senozhatsky@gmail.com>: > > On (10/24/12 20:06), Oleg Nesterov wrote: > >> On 10/24, Sergey Senozhatsky wrote: > >> > > >> > small question, > >> > > >> > ptrace_notify() and forward calls are able to both indirectly and directly call schedule(), > >> > /* direct call from ptrace_stop()*/, > >> > should, in this case, rcu_user_enter() be called before tracehook_report_syscall_exit(regs, step) > >> > and ptrace chain? > >> > >> Well, I don't really understand this magic... but why? > >> > > > > My understanding is (I may be wrong) that we can schedule() from ptrace chain to > > some arbitrary task, which will continue its execution from the point where RCU assumes > > CPU as not idle, while CPU in fact still in idle state -- no one said rcu_idle_exit() > > (or similar) prior to schedule() call. > > Yeah but when we are in syscall_trace_leave(), the CPU shouldn't be in > RCU idle mode. That's where the bug is. How do you manage to trigger > this bug? >
strace -f <anything>
-ss
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