From: Guilherme G. Piccoli gpiccoli@igalia.com
[ Upstream commit 829632dae8321787525ee37dc4828bbe6edafdae ]
The panic notifiers' callbacks execute in an atomic context, with interrupts/preemption disabled, and all CPUs not running the panic function are off, so it's very dangerous to wait on a regular spinlock, there's a risk of deadlock.
Refactor the panic notifier of parisc/power driver to make use of spin_trylock - for that, we've added a second version of the soft-power function. Also, some comments were reorganized and trailing white spaces, useless header inclusion and blank lines were removed.
Cc: "James E.J. Bottomley" James.Bottomley@HansenPartnership.com Cc: Jeroen Roovers jer@xs4all.nl Acked-by: Helge Deller deller@gmx.de # parisc Signed-off-by: Guilherme G. Piccoli gpiccoli@igalia.com Signed-off-by: Helge Deller deller@gmx.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/parisc/include/asm/pdc.h | 1 + arch/parisc/kernel/firmware.c | 27 +++++++++++++++++++++++---- drivers/parisc/power.c | 16 ++++++++++------ 3 files changed, 34 insertions(+), 10 deletions(-)
diff --git a/arch/parisc/include/asm/pdc.h b/arch/parisc/include/asm/pdc.h index b388d81765883..2f48e0a80d9c6 100644 --- a/arch/parisc/include/asm/pdc.h +++ b/arch/parisc/include/asm/pdc.h @@ -81,6 +81,7 @@ 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 8e5a906df9175..5385e0fe98426 100644 --- a/arch/parisc/kernel/firmware.c +++ b/arch/parisc/kernel/firmware.c @@ -1158,15 +1158,18 @@ 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 on spin_trylock to prevent deadlock + * on panic path. */ int pdc_soft_power_button(int sw_control) { @@ -1180,6 +1183,22 @@ 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 456776bd8ee66..6f5e5f0230d39 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; }