Messages in this thread | | | Date | Sat, 19 Oct 2013 15:16:58 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH 2/6] x86: allow to call text_poke_bp during boot |
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On Sun, 20 Oct 2013 00:02:32 +0900 Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
> (2013/10/18 23:27), Petr Mladek wrote: > > We would like to use text_poke_bp in ftrace. It might be called also during > > boot when the interupts are disabled. We need to enable them for syncing > > the cores on each CPU. Otherwise, there might be a deadlock, see the > > warning in "smp_call_function_many", kernel/smp.c:371. > > Steven, is this really needed? > I think if this is the special use(e.g. boottime test), > we'd better to run it after boot... >
It's used to convert the calls to mcount to nops. But maybe a better thing to do is to check if we only have a single CPU:
static void run_sync(void) { if (num_online_cpus() != 1) on_each_cpu(do_sync_core, NULL, 1); }
I believe that the only time we call this function with interrupts disabled is before SMP is set up. Thus, the above change would handle that case.
-- Steve
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