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Message-Id: <20220719195325.402745-8-gpiccoli@igalia.com>
Date: Tue, 19 Jul 2022 16:53:20 -0300
From: "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To: akpm@...ux-foundation.org, bhe@...hat.com, pmladek@...e.com,
kexec@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
netdev@...r.kernel.org, x86@...nel.org, kernel-dev@...lia.com,
kernel@...ccoli.net, halves@...onical.com, fabiomirmar@...il.com,
alejandro.j.jimenez@...cle.com, andriy.shevchenko@...ux.intel.com,
arnd@...db.de, bp@...en8.de, corbet@....net,
d.hatayama@...fujitsu.com, dave.hansen@...ux.intel.com,
dyoung@...hat.com, feng.tang@...el.com, gregkh@...uxfoundation.org,
mikelley@...rosoft.com, hidehiro.kawai.ez@...achi.com,
jgross@...e.com, john.ogness@...utronix.de, keescook@...omium.org,
luto@...nel.org, mhiramat@...nel.org, mingo@...hat.com,
paulmck@...nel.org, peterz@...radead.org, rostedt@...dmis.org,
senozhatsky@...omium.org, stern@...land.harvard.edu,
tglx@...utronix.de, vgoyal@...hat.com, vkuznets@...hat.com,
will@...nel.org, "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
linux-parisc@...r.kernel.org,
"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
Helge Deller <deller@....de>
Subject: [PATCH v2 07/13] parisc: Replace regular spinlock with spin_trylock on panic path
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@...senPartnership.com>
Acked-by: Helge Deller <deller@....de> # parisc
Signed-off-by: Guilherme G. Piccoli <gpiccoli@...lia.com>
---
V2:
- Added Helge's ACK - thanks!
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;
--
2.37.1
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