(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...
Thank you,
>
> This change is taken from the current code in arch/x86/kernel/ftrace.c.
>
> Signed-off-by: Petr Mladek <pmla...@suse.cz>
> ---
> arch/x86/kernel/alternative.c | 20 +++++++++++++++++---
> 1 file changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index f714316..13cae15 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -629,6 +629,20 @@ static void do_sync_core(void *info)
> sync_core();
> }
>
> +static void run_sync(void)
> +{
> + int enable_irqs = irqs_disabled();
> +
> + /* We may be called with interrupts disbled (on bootup). */
> + if (enable_irqs)
> + local_irq_enable();
> +
> + on_each_cpu(do_sync_core, NULL, 1);
> +
> + if (enable_irqs)
> + local_irq_disable();
> +}
> +
> static bool bp_patching_in_progress;
> static void *bp_int3_handler, *bp_int3_addr;
>
> @@ -688,7 +702,7 @@ void *text_poke_bp(void *addr, const void *opcode, size_t
> len, void *handler)
>
> text_poke_part(addr, &int3, sizeof(int3));
>
> - on_each_cpu(do_sync_core, NULL, 1);
> + run_sync();
>
> if (len - sizeof(int3) > 0) {
> /* patch all but the first byte */
> @@ -700,13 +714,13 @@ void *text_poke_bp(void *addr, const void *opcode,
> size_t len, void *handler)
> * not necessary and we'd be safe even without it. But
> * better safe than sorry (plus there's not only Intel).
> */
> - on_each_cpu(do_sync_core, NULL, 1);
> + run_sync();
> }
>
> /* patch the first byte */
> text_poke_part(addr, opcode, sizeof(int3));
>
> - on_each_cpu(do_sync_core, NULL, 1);
> + run_sync();
>
> bp_patching_in_progress = false;
> smp_wmb();
>
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu...@hitachi.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
