Re: [PATCH 12/30] parisc: Replace regular spinlock with spin_trylock on panic path

Guilherme G. Piccoli
2022-04-29T14:36:30Z

On 28/04/2022 13:55, Helge Deller wrote:
> [...]
> You may add:
> Acked-by: Helge Deller <deller@gmx.de> # parisc
>
> Helge

Thanks Helge, added!
Cheers,

Guilherme

>
>
>> ---
>> arch/parisc/include/asm/pdc.h | 1 +
>> arch/parisc/kernel/firmware.c | 27 +++++++++++++++++++++++----
>> drivers/parisc/power.c | 17 ++++++++++-------
>> 3 files changed, 34 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/parisc/include/asm/pdc.h b/arch/parisc/include/asm/pdc.h
>> index b643092d4b98..7a106008e258 100644
>> --- a/arch/parisc/include/asm/pdc.h
>> +++ b/arch/parisc/include/asm/pdc.h
>> @@ -83,6 +83,7 @@ int pdc_do_firm_test_reset(unsigned long ftc_bitmap);
>> int pdc_do_reset(void);
>> int pdc_soft_power_info(unsigned long *power_reg);
>> int pdc_soft_power_button(int sw_control);
>> +int pdc_soft_power_button_panic(int sw_control);
>> void pdc_io_reset(void);
>> void pdc_io_reset_devices(void);
>> int pdc_iodc_getc(void);
>> diff --git a/arch/parisc/kernel/firmware.c b/arch/parisc/kernel/firmware.c
>> index 6a7e315bcc2e..0e2f70b592f4 100644
>> --- a/arch/parisc/kernel/firmware.c
>> +++ b/arch/parisc/kernel/firmware.c
>> @@ -1232,15 +1232,18 @@ int __init pdc_soft_power_info(unsigned long *power_reg)
>> }
>>
>> /*
>> - * pdc_soft_power_button - Control the soft power button behaviour
>> - * @sw_control: 0 for hardware control, 1 for software control
>> + * pdc_soft_power_button{_panic} - Control the soft power button behaviour
>> + * @sw_control: 0 for hardware control, 1 for software control
>> *
>> *
>> * This PDC function places the soft power button under software or
>> * hardware control.
>> - * Under software control the OS may control to when to allow to shut
>> - * down the system. Under hardware control pressing the power button
>> + * Under software control the OS may control to when to allow to shut
>> + * down the system. Under hardware control pressing the power button
>> * powers off the system immediately.
>> + *
>> + * The _panic version relies in spin_trylock to prevent deadlock
>> + * on panic path.
>> */
>> int pdc_soft_power_button(int sw_control)
>> {
>> @@ -1254,6 +1257,22 @@ int pdc_soft_power_button(int sw_control)
>> return retval;
>> }
>>
>> +int pdc_soft_power_button_panic(int sw_control)
>> +{
>> + int retval;
>> + unsigned long flags;
>> +
>> + if (!spin_trylock_irqsave(&pdc_lock, flags)) {
>> + pr_emerg("Couldn't enable soft power button\n");
>> + return -EBUSY; /* ignored by the panic notifier */
>> + }
>> +
>> + retval = mem_pdc_call(PDC_SOFT_POWER, PDC_SOFT_POWER_ENABLE, __pa(pdc_result), sw_control);
>> + spin_unlock_irqrestore(&pdc_lock, flags);
>> +
>> + return retval;
>> +}
>> +
>> /*
>> * pdc_io_reset - Hack to avoid overlapping range registers of Bridges devices.
>> * Primarily a problem on T600 (which parisc-linux doesn't support) but
>> diff --git a/drivers/parisc/power.c b/drivers/parisc/power.c
>> index 456776bd8ee6..8512884de2cf 100644
>> --- a/drivers/parisc/power.c
>> +++ b/drivers/parisc/power.c
>> @@ -37,7 +37,6 @@
>> #include <linux/module.h>
>> #include <linux/init.h>
>> #include <linux/kernel.h>
>> -#include <linux/notifier.h>
>> #include <linux/panic_notifier.h>
>> #include <linux/reboot.h>
>> #include <linux/sched/signal.h>
>> @@ -175,16 +174,21 @@ static void powerfail_interrupt(int code, void *x)
>>
>>
>>
>> -/* parisc_panic_event() is called by the panic handler.
>> - * As soon as a panic occurs, our tasklets above will not be
>> - * executed any longer. This function then re-enables the
>> - * soft-power switch and allows the user to switch off the system
>> +/*
>> + * parisc_panic_event() is called by the panic handler.
>> + *
>> + * As soon as a panic occurs, our tasklets above will not
>> + * be executed any longer. This function then re-enables
>> + * the soft-power switch and allows the user to switch off
>> + * the system. We rely in pdc_soft_power_button_panic()
>> + * since this version spin_trylocks (instead of regular
>> + * spinlock), preventing deadlocks on panic path.
>> */
>> static int parisc_panic_event(struct notifier_block *this,
>> unsigned long event, void *ptr)
>> {
>> /* re-enable the soft-power switch */
>> - pdc_soft_power_button(0);
>> + pdc_soft_power_button_panic(0);
>> return NOTIFY_DONE;
>> }
>>
>> @@ -193,7 +197,6 @@ static struct notifier_block parisc_panic_block = {
>> .priority = INT_MAX,
>> };
>>
>> -
>> static int __init power_init(void)
>> {
>> unsigned long ret;
>