Messages in this thread | | | Date | Thu, 25 May 2017 08:15:55 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC PATCH tip/master] kprobes: Use synchronize_rcu_tasks() for optprobe wit CONFIG_PREEMPT |
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* Masami Hiramatsu <mhiramat@kernel.org> wrote:
> --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -377,6 +377,23 @@ static inline void copy_kprobe(struct kprobe *ap, struct kprobe *p) > static bool kprobes_allow_optimization; > > /* > + * Synchronizing wait on trampline code for interrupted tasks/threads. > + * Since the threads running on dynamically allocated trampline code > + * can be interrupted, kprobes has to wait for those tasks back on > + * track and scheduled. If the kernel is preemptive, the thread can be > + * preempted by other tasks on the trampoline too. For such case, this > + * calls synchronize_rcu_tasks() to wait for those tasks back on track. > + */ > +static void synchronize_on_trampoline(void) > +{ > +#ifdef CONFIG_PREEMPT > + synchronize_rcu_tasks(); > +#else > + synchronize_sched(); > +#endif > +}
So that's really unacceptably ugly.
Paul, I still question the need to have tasks-RCU as a Kconfig distinction, _especially_ if its API usage results in such ugly secondary #ifdefs...
Why isn't there a single synchronize_rcu_tasks() API function, which does what is expected, where the _RCU_ code figures out how to implement it?
I.e.:
- There should be no user configurable TASKS_RCU Kconfig setting - at most a helper Kconfig that is automatically selected by the RCU code itself.
- Both ftrace andkprobes would use a simple synchronize_rcu_tasks() call.
Thanks,
Ingo
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