This is a note to let you know that I've just added the patch titled
parisc: Replace regular spinlock with spin_trylock on panic path
to the 6.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
parisc-replace-regular-spinlock-with-spin_trylock-on.patch
and it can be found in the queue-6.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9ab368cd8ced32746b051bedabcfccc0e5e1ad5a
Author: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
Date: Mon Feb 20 18:11:05 2023 -0300
parisc: Replace regular spinlock with spin_trylock on panic path
[ 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@xxxxxxxxxxxxxxxxxxxxx>
Cc: Jeroen Roovers <jer@xxxxxxxxx>
Acked-by: Helge Deller <deller@xxxxxx> # parisc
Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/parisc/include/asm/pdc.h b/arch/parisc/include/asm/pdc.h
index 40793bef8429f..2b4fad8328e85 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 6817892a2c585..cc124d9f1f7f7 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 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;
}
