diff options
| author |   Vitaly Kuznetsov <vkuznets@redhat.com> | 2021-03-24 16:22:19 +0100 |
|---|---|---|
| committer |   Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2021-04-01 13:37:55 +0200 |
| commit | 8cdddd182bd7befae6af49c5fd612893f55d6ccb (patch) | |
| tree | d082d5e17f703d2d18dcd6b729e734b592e47849 /drivers | |
| parent | Linux 5.12-rc5 (diff) | |
| download | linux-dev-8cdddd182bd7befae6af49c5fd612893f55d6ccb.tar.xz linux-dev-8cdddd182bd7befae6af49c5fd612893f55d6ccb.zip | |
ACPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()
Commit 496121c02127 ("ACPI: processor: idle: Allow probing on platforms
with one ACPI C-state") broke CPU0 hotplug on certain systems, e.g.
I'm observing the following on AWS Nitro (e.g r5b.xlarge but other
instance types are affected as well):
# echo 0 > /sys/devices/system/cpu/cpu0/online
# echo 1 > /sys/devices/system/cpu/cpu0/online
<10 seconds delay>
-bash: echo: write error: Input/output error
In fact, the above mentioned commit only revealed the problem and did
not introduce it. On x86, to wakeup CPU an NMI is being used and
hlt_play_dead()/mwait_play_dead() loops are prepared to handle it:
/*
* If NMI wants to wake up CPU0, start CPU0.
*/
if (wakeup_cpu0())
start_cpu0();
cpuidle_play_dead() -> acpi_idle_play_dead() (which is now being called on
systems where it wasn't called before the above mentioned commit) serves
the same purpose but it doesn't have a path for CPU0. What happens now on
wakeup is:
- NMI is sent to CPU0
- wakeup_cpu0_nmi() works as expected
- we get back to while (1) loop in acpi_idle_play_dead()
- safe_halt() puts CPU0 to sleep again.
The straightforward/minimal fix is add the special handling for CPU0 on x86
and that's what the patch is doing.
Fixes: 496121c02127 ("ACPI: processor: idle: Allow probing on platforms with one ACPI C-state")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: 5.10+ <stable@vger.kernel.org> # 5.10+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/acpi/processor_idle.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index d93e400940a3..768a6b4d2368 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -29,6 +29,7 @@ */ #ifdef CONFIG_X86 #include <asm/apic.h> +#include <asm/cpu.h> #endif #define _COMPONENT ACPI_PROCESSOR_COMPONENT @@ -541,6 +542,12 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index) wait_for_freeze(); } else return -ENODEV; + +#if defined(CONFIG_X86) && defined(CONFIG_HOTPLUG_CPU) + /* If NMI wants to wake up CPU0, start CPU0. */ + if (wakeup_cpu0()) + start_cpu0(); +#endif } /* Never reached */ |