On Mon, Jul 30, 2012 at 03:15:59PM +0800, Feng Tang wrote:
> Hi All,
>
> When I debugged a suspend/resume bug, I found that tick_broadcast_mask is not
> restored for a CPU after it is offline/onlined since kernel 3.4, while it's
> fine for 3.3.
Could you please try 3.5?
> Further check show it is caused by the commit 9505626d7bfe
> ACPI: Fix unprotected smp_processor_id() in
> acpi_processor_cst_has_changed()
>
> The acpi_processor_cst_has_changed() function is invoked from a
> CPU_ONLINE or CPU_DEAD function, which might well execute on CPU 0
> even though the CPU being hotplugged is some other CPU. In addition,
> acpi_processor_cst_has_changed() invokes smp_processor_id() without
> protection, resulting in splats when onlining CPUs.
>
> This commit therefore changes the smp_processor_id() to pr->id, as is
> used elsewhere in the code, for example, in acpi_processor_add().
>
> Signed-off-by: Paul E. McKenney <paul.mcken...@linaro.org>
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 0e8e2de..9e57b06 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -1159,8 +1159,7 @@ int acpi_processor_cst_has_changed(struct
> acpi_processor *pr)
> * to make the code that updates C-States be called once.
> */
>
> - if (smp_processor_id() == 0 &&
> - cpuidle_get_driver() == &acpi_idle_driver) {
> + if (pr->id == 0 && cpuidle_get_driver() == &acpi_idle_driver) {
>
> cpuidle_pause_and_lock();
> /* Protect against cpu-hotplug */
>
> The root cause is acpi_processor_cst_has_changed() will also be called when
> cpu_up() is run on cpu 0 to boot up other cpu, this commit will prevent the
> following code be run for that cpu, which triggers some side effect like the
> broadcast_mask is not restored.
>
> I raise this problem up and I don't if revert is a good solution here.
Indeed, that would re-introduce the splats from unprotected use of
smp_processor_id(). :-(
Thanx, Paul
--
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/
