From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
To: akpm@linux-foundation.org, bhe@redhat.com, pmladek@suse.com,
kexec@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org,
netdev@vger.kernel.org, x86@kernel.org, kernel-dev@igalia.com,
kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com,
alejandro.j.jimenez@oracle.com,
andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de,
corbet@lwn.net, d.hatayama@jp.fujitsu.com,
dave.hansen@linux.intel.com, dyoung@redhat.com,
feng.tang@intel.com, gregkh@linuxfoundation.org,
mikelley@microsoft.com, hidehiro.kawai.ez@hitachi.com,
jgross@suse.com, john.ogness@linutronix.de,
keescook@chromium.org, luto@kernel.org, mhiramat@kernel.org,
mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org,
rostedt@goodmis.org, senozhatsky@chromium.org,
stern@rowland.harvard.edu, tglx@linutronix.de, vgoyal@redhat.com,
vkuznets@redhat.com, will@kernel.org, xuqiang36@huawei.com,
"Guilherme G. Piccoli" <gpiccoli@igalia.com>,
linux-parisc@vger.kernel.org,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
Jeroen Roovers <jer@xs4all.nl>, Helge Deller <deller@gmx.de>
Subject: [PATCH V3 05/11] parisc: Replace regular spinlock with spin_trylock on panic path
Date: Fri, 19 Aug 2022 19:17:25 -0300 [thread overview]
Message-ID: <20220819221731.480795-6-gpiccoli@igalia.com> (raw)
In-Reply-To: <20220819221731.480795-1-gpiccoli@igalia.com>
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>
---
V3:
- s/in/on as per Jeroen's suggestion - thanks!
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..3b1f7641e3c9 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;
--
2.37.2
prev parent reply other threads:[~2022-08-19 22:22 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-19 22:17 [PATCH V3 00/11] The panic notifiers refactor - fixes/clean-ups (V3) Guilherme G. Piccoli
2022-08-19 22:17 ` Guilherme G. Piccoli [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220819221731.480795-6-gpiccoli@igalia.com \
--to=gpiccoli@igalia.com \
--cc=James.Bottomley@HansenPartnership.com \
--cc=akpm@linux-foundation.org \
--cc=alejandro.j.jimenez@oracle.com \
--cc=andriy.shevchenko@linux.intel.com \
--cc=arnd@arndb.de \
--cc=bhe@redhat.com \
--cc=bp@alien8.de \
--cc=corbet@lwn.net \
--cc=d.hatayama@jp.fujitsu.com \
--cc=dave.hansen@linux.intel.com \
--cc=deller@gmx.de \
--cc=dyoung@redhat.com \
--cc=fabiomirmar@gmail.com \
--cc=feng.tang@intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=halves@canonical.com \
--cc=hidehiro.kawai.ez@hitachi.com \
--cc=jer@xs4all.nl \
--cc=jgross@suse.com \
--cc=john.ogness@linutronix.de \
--cc=keescook@chromium.org \
--cc=kernel-dev@igalia.com \
--cc=kernel@gpiccoli.net \
--cc=kexec@lists.infradead.org \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-parisc@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mhiramat@kernel.org \
--cc=mikelley@microsoft.com \
--cc=mingo@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=senozhatsky@chromium.org \
--cc=stern@rowland.harvard.edu \
--cc=tglx@linutronix.de \
--cc=vgoyal@redhat.com \
--cc=vkuznets@redhat.com \
--cc=will@kernel.org \
--cc=x86@kernel.org \
--cc=xuqiang36@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).