| Message ID | 20230220211105.151401-1-gpiccoli@igalia.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | [v4] parisc: Replace regular spinlock with spin_trylock on panic path | expand |
On 2/20/23 22:11, Guilherme G. Piccoli wrote: > 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> > > --- > V4: > - rebase against v6.2 (build-tested). > > V3: > - s/in/on as per Jeroen's suggestion - thanks! > > V2: > - Added Helge's ACK - thanks! > > > Hey Helge, this is the V4 - just rebased and build-tested on v6.2. > I remember we discussed the possibility of this getting merged through > the series I've submitted [0], but happens the series is "gone", most of > the patches were picked by maintainers, others I'm dropping. This is really > a standalone fix, similar ones were merged in other notifiers. > > I'd appreciate if you/James could pick it for the next kernel, there's no > rush at all, but there's also no series we could throw this patch to get > merged with heh > > Thanks in advance, > Guilherme Thank you Guilherme! I've now picked it up in the parisc-for-next tree. Helge > > [0] https://lore.kernel.org/lkml/43de5653-7587-3e8e-274c-b2729649d0fd@gmx.de/ > > > 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 40793bef8429..2b4fad8328e8 100644 > --- a/arch/parisc/include/asm/pdc.h > +++ b/arch/parisc/include/asm/pdc.h > @@ -80,6 +80,7 @@ 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 6817892a2c58..cc124d9f1f7f 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 on 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;
On 28/02/2023 15:45, Helge Deller wrote: > [...] > Thank you Guilherme! > > I've now picked it up in the parisc-for-next tree. > > Helge Thanks a lot Helge, much appreciated! Cheers, Guilherme
diff --git a/arch/parisc/include/asm/pdc.h b/arch/parisc/include/asm/pdc.h index 40793bef8429..2b4fad8328e8 100644 --- a/arch/parisc/include/asm/pdc.h +++ b/arch/parisc/include/asm/pdc.h @@ -80,6 +80,7 @@ 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 6817892a2c58..cc124d9f1f7f 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 on 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;