Messages in this thread Patch in this message | | | Date | Mon, 30 Jul 2012 16:43:44 +0800 | Subject | [Regression][Bisected] tick_broadcast_mask is not restored after a CPU is offline/onlined | From | Feng Tang <> |
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Hi All,
[seems the email from my intel email address didn't hit the list, resend with gmail, sorry for the noise]
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.
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.mckenney@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.
Thanks, Feng
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