Re: [PATCH v4] panic: Avoid the extra noise dmesg
Hi Petr,
Thanks for your review.
On Wed, Feb 20, 2019 at 02:43:44PM +0100, Petr Mladek wrote:
> On Fri 2019-02-15 13:56:54, Feng Tang wrote:
> > Hi all,
> >
> > On Tue, Dec 11, 2018 at 09:32:30AM +0100, Petr Mladek wrote:
> > > On Mon 2018-12-10 10:49:22, Kees Cook wrote:
> > > > On Mon, Dec 10, 2018 at 10:17 AM Steven Rostedt
> > > > wrote:
> > > > >
> > > > > On Fri, 7 Dec 2018 17:51:19 +0800
> > > > > Feng Tang wrote:
> > > > >
> > > > > > When kernel panic happens, it will first print the panic call stack,
> > > > > > then the ending msg like:
> > > > > >
> > > > > > [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception
> > > > > > [ 35.749975] [ cut here ]
> > > > > >
> > > > > > The above message are very useful for debugging.
> > > > > >
> > > > > > But if system is configured to not reboot on panic, say the
> > > > > > "panic_timeout"
> > > > > > parameter equals 0, it will likely print out many noisy message like
> > > > > > WARN() call stack for each and every CPU except the panic one,
> > > > > > messages
> > > > > > like below:
> >
> > So currently, there are 2 proposals:
> > 1. this v4 patch of "panic_keep_irq_on" flag (default off to be same
> >as the current kernel behavior)
> > 2. Petr's suggestion of adding a flag to suppress printk after enterring
> >late panic phase (blinking time), while keeping the sysrq printk
> >working.
> >
> > Following is the draft patch based on Petr's suggestion:
> >
> > Please review, thanks. I'm fine with both solutions.
> >
> > - Feng
> >
> > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> > index 1f03078..8921fed 100644
> > --- a/drivers/tty/sysrq.c
> > +++ b/drivers/tty/sysrq.c
> > @@ -528,6 +528,11 @@ void __handle_sysrq(int key, bool check_mask)
> > struct sysrq_key_op *op_p;
> > int orig_log_level;
> > int i;
> > + int old_val;
> > +
> > + /* save the old panic printk flag */
>
> The comment is not needed. It is obvious.
ok, will remove.
>
> > + old_val = panic_suppress_printk;
>
> s/old_val/orig_panic_suppress_printk/ to follow
> the naming of orig_log_level.
Ok.
>
> > + panic_suppress_printk = 1;
>
> We want to enable the messages in sysrq. This should be:
>
> panic_suppress_printk = 0;
Yes, will do.
>
> > rcu_sysrq_start();
> > rcu_read_lock();
> > @@ -574,6 +579,8 @@ void __handle_sysrq(int key, bool check_mask)
> > }
> > rcu_read_unlock();
> > rcu_sysrq_end();
> > +
> > + panic_suppress_printk = old_val;
> > }
> >
> > void handle_sysrq(int key)
> > diff --git a/kernel/panic.c b/kernel/panic.c
> > index f121e6b..0cd3a1b 100644
> > --- a/kernel/panic.c
> > +++ b/kernel/panic.c
> > @@ -326,6 +328,7 @@ void panic(const char *fmt, ...)
> > }
> > #endif
> > pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
>
> /* Do not scroll important messages with errors from blinking code. */
Will add the comment, with one minor chanage that the noisy messages may
also come from other places.
>
> > + panic_suppress_printk = 1;
> > local_irq_enable();
> > for (i = 0; ; i += PANIC_TIMER_STEP) {
> > touch_softlockup_watchdog();
> > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> > index d3d1703..c27bbf5 100644
> > --- a/kernel/printk/printk.c
> > +++ b/kernel/printk/printk.c
> > @@ -1987,6 +1987,9 @@ asmlinkage __visible int printk(const char *fmt, ...)
> > va_list args;
> > int r;
>
> /* Suppress messages from panic blinking code. */
Ditto.
> > + if (unlikely(panic_suppress_printk))
> > + return 0;
>
> This should go to vprintk_emit() so that it works for all
> printk() interfaces.
Ok, will do.
Thanks,
Feng
>
> > +
> > va_start(args, fmt);
> > r = vprintk_func(fmt, args);
> > va_end(args);
>
> Best Regards,
> Petr
Re: [PATCH v4] panic: Avoid the extra noise dmesg
On Fri 2019-02-15 13:56:54, Feng Tang wrote:
> Hi all,
>
> On Tue, Dec 11, 2018 at 09:32:30AM +0100, Petr Mladek wrote:
> > On Mon 2018-12-10 10:49:22, Kees Cook wrote:
> > > On Mon, Dec 10, 2018 at 10:17 AM Steven Rostedt
> > > wrote:
> > > >
> > > > On Fri, 7 Dec 2018 17:51:19 +0800
> > > > Feng Tang wrote:
> > > >
> > > > > When kernel panic happens, it will first print the panic call stack,
> > > > > then the ending msg like:
> > > > >
> > > > > [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception
> > > > > [ 35.749975] [ cut here ]
> > > > >
> > > > > The above message are very useful for debugging.
> > > > >
> > > > > But if system is configured to not reboot on panic, say the
> > > > > "panic_timeout"
> > > > > parameter equals 0, it will likely print out many noisy message like
> > > > > WARN() call stack for each and every CPU except the panic one,
> > > > > messages
> > > > > like below:
>
> So currently, there are 2 proposals:
> 1. this v4 patch of "panic_keep_irq_on" flag (default off to be same
>as the current kernel behavior)
> 2. Petr's suggestion of adding a flag to suppress printk after enterring
>late panic phase (blinking time), while keeping the sysrq printk
>working.
>
> Following is the draft patch based on Petr's suggestion:
>
> Please review, thanks. I'm fine with both solutions.
>
> - Feng
>
> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
> index 1f03078..8921fed 100644
> --- a/drivers/tty/sysrq.c
> +++ b/drivers/tty/sysrq.c
> @@ -528,6 +528,11 @@ void __handle_sysrq(int key, bool check_mask)
> struct sysrq_key_op *op_p;
> int orig_log_level;
> int i;
> + int old_val;
> +
> + /* save the old panic printk flag */
The comment is not needed. It is obvious.
> + old_val = panic_suppress_printk;
s/old_val/orig_panic_suppress_printk/ to follow
the naming of orig_log_level.
> + panic_suppress_printk = 1;
We want to enable the messages in sysrq. This should be:
panic_suppress_printk = 0;
> rcu_sysrq_start();
> rcu_read_lock();
> @@ -574,6 +579,8 @@ void __handle_sysrq(int key, bool check_mask)
> }
> rcu_read_unlock();
> rcu_sysrq_end();
> +
> + panic_suppress_printk = old_val;
> }
>
> void handle_sysrq(int key)
> diff --git a/kernel/panic.c b/kernel/panic.c
> index f121e6b..0cd3a1b 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -326,6 +328,7 @@ void panic(const char *fmt, ...)
> }
> #endif
> pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
/* Do not scroll important messages with errors from blinking code. */
> + panic_suppress_printk = 1;
> local_irq_enable();
> for (i = 0; ; i += PANIC_TIMER_STEP) {
> touch_softlockup_watchdog();
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index d3d1703..c27bbf5 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -1987,6 +1987,9 @@ asmlinkage __visible int printk(const char *fmt, ...)
> va_list args;
> int r;
/* Suppress messages from panic blinking code. */
> + if (unlikely(panic_suppress_printk))
> + return 0;
This should go to vprintk_emit() so that it works for all
printk() interfaces.
> +
> va_start(args, fmt);
> r = vprintk_func(fmt, args);
> va_end(args);
Best Regards,
Petr
Re: [PATCH v4] panic: Avoid the extra noise dmesg
Hi all,
On Tue, Dec 11, 2018 at 09:32:30AM +0100, Petr Mladek wrote:
> On Mon 2018-12-10 10:49:22, Kees Cook wrote:
> > On Mon, Dec 10, 2018 at 10:17 AM Steven Rostedt wrote:
> > >
> > > On Fri, 7 Dec 2018 17:51:19 +0800
> > > Feng Tang wrote:
> > >
> > > > When kernel panic happens, it will first print the panic call stack,
> > > > then the ending msg like:
> > > >
> > > > [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception
> > > > [ 35.749975] [ cut here ]
> > > >
> > > > The above message are very useful for debugging.
> > > >
> > > > But if system is configured to not reboot on panic, say the
> > > > "panic_timeout"
> > > > parameter equals 0, it will likely print out many noisy message like
> > > > WARN() call stack for each and every CPU except the panic one, messages
> > > > like below:
> > >
> > >
> > > > Keeping the interrupt disabled will avoid the noisy message.
> > > >
> > > > When code runs to this point, it means user has chosed to not reboot, or
> > > > do any special handling by using the panic notifier method, the only
> > > > reason
> > > > to enable the interrupt may be sysrq migic key and panic_blink function
> > > > (though may not work even with irq enabled).
> > > >
> > > > So make the irq disabled by default and add a cmdline parameter
> > > > "panic_keep_irq_on" to turn it on when needed.
> > > >
> > > > Signed-off-by: Feng Tang
> > > >
> > >
> > > Acked-by: Steven Rostedt (VMware)
> >
> > I'm fine with the new boot param, but I think we need to leave it how
> > it was by default: systems that want to see the blinking aren't going
> > to have a screen to read about what boot param they need to add.
> > Currently, we'll blink and spew extra warnings. With this patch we'll
> > not blink and not spew: a headless machine will have no indication
> > that a panic happened.
>
> Just to be sure, in case, you did not follow the other long
> discussion.
>
> I had an alternative approach to switch printk() into nop at
> this panic() stage. It can be restored when sysrq is triggered.
> This approach allows to keep blinking and sysrq working. People
> debugging the blinking would need to block this change but it
> should be rare.
>
> I do not resist on my solution. It looks a bit hacky. But it
> is simple and rather straightforward.
Sorry for the late response.
So currently, there are 2 proposals:
1. this v4 patch of "panic_keep_irq_on" flag (default off to be same
as the current kernel behavior)
2. Petr's suggestion of adding a flag to suppress printk after enterring
late panic phase (blinking time), while keeping the sysrq printk
working.
Following is the draft patch based on Petr's suggestion:
Please review, thanks. I'm fine with both solutions.
- Feng
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 1f03078..8921fed 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -528,6 +528,11 @@ void __handle_sysrq(int key, bool check_mask)
struct sysrq_key_op *op_p;
int orig_log_level;
int i;
+ int old_val;
+
+ /* save the old panic printk flag */
+ old_val = panic_suppress_printk;
+ panic_suppress_printk = 1;
rcu_sysrq_start();
rcu_read_lock();
@@ -574,6 +579,8 @@ void __handle_sysrq(int key, bool check_mask)
}
rcu_read_unlock();
rcu_sysrq_end();
+
+ panic_suppress_printk = old_val;
}
void handle_sysrq(int key)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 8f0e68e..4120f3a 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -534,6 +534,7 @@ extern int panic_on_io_nmi;
extern int panic_on_warn;
extern int sysctl_panic_on_rcu_stall;
extern int sysctl_panic_on_stackoverflow;
+extern int panic_suppress_printk;
extern bool crash_kexec_post_notifiers;
diff --git a/kernel/panic.c b/kernel/panic.c
index f121e6b..0cd3a1b 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -46,6 +46,8 @@ int panic_on_warn __read_mostly;
int panic_timeout = CONFIG_PANIC_TIMEOUT;
EXPORT_SYMBOL_GPL(panic_timeout);
+int panic_suppress_printk;
+
#define PANIC_PRINT_TASK_INFO 0x0001
#define PANIC_PRINT_MEM_INFO 0x0002
#define PANIC_PRINT_TIMER_INFO 0x0004
@@ -326,6 +328,7 @@ void panic(const char *fmt, ...)
}
#endif
pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
+ panic_suppress_printk = 1;
local_irq_enable();
for (i = 0; ; i += PANIC_TIMER_STEP) {
touch_softlockup_watchdog();
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d3d1703..c27bbf5 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1987,6 +1987,9 @@ asmlinkage __visible int printk(const char *fmt, ...)
va_list args;
int r;
+ if (unlikely(panic_suppress_printk))
+ return 0;
+
va_start(args, fmt);
r = vprintk_func(fmt, args);
Re: [PATCH v4] panic: Avoid the extra noise dmesg
On Mon 2018-12-10 10:49:22, Kees Cook wrote: > On Mon, Dec 10, 2018 at 10:17 AM Steven Rostedt wrote: > > > > On Fri, 7 Dec 2018 17:51:19 +0800 > > Feng Tang wrote: > > > > > When kernel panic happens, it will first print the panic call stack, > > > then the ending msg like: > > > > > > [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception > > > [ 35.749975] [ cut here ] > > > > > > The above message are very useful for debugging. > > > > > > But if system is configured to not reboot on panic, say the > > > "panic_timeout" > > > parameter equals 0, it will likely print out many noisy message like > > > WARN() call stack for each and every CPU except the panic one, messages > > > like below: > > > > > > > Keeping the interrupt disabled will avoid the noisy message. > > > > > > When code runs to this point, it means user has chosed to not reboot, or > > > do any special handling by using the panic notifier method, the only > > > reason > > > to enable the interrupt may be sysrq migic key and panic_blink function > > > (though may not work even with irq enabled). > > > > > > So make the irq disabled by default and add a cmdline parameter > > > "panic_keep_irq_on" to turn it on when needed. > > > > > > Signed-off-by: Feng Tang > > > > > > > Acked-by: Steven Rostedt (VMware) > > I'm fine with the new boot param, but I think we need to leave it how > it was by default: systems that want to see the blinking aren't going > to have a screen to read about what boot param they need to add. > Currently, we'll blink and spew extra warnings. With this patch we'll > not blink and not spew: a headless machine will have no indication > that a panic happened. Just to be sure, in case, you did not follow the other long discussion. I had an alternative approach to switch printk() into nop at this panic() stage. It can be restored when sysrq is triggered. This approach allows to keep blinking and sysrq working. People debugging the blinking would need to block this change but it should be rare. I do not resist on my solution. It looks a bit hacky. But it is simple and rather straightforward. Best Regards, Petr
Re: [PATCH v4] panic: Avoid the extra noise dmesg
On Mon, Dec 10, 2018 at 10:17 AM Steven Rostedt wrote: > > On Fri, 7 Dec 2018 17:51:19 +0800 > Feng Tang wrote: > > > When kernel panic happens, it will first print the panic call stack, > > then the ending msg like: > > > > [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception > > [ 35.749975] [ cut here ] > > > > The above message are very useful for debugging. > > > > But if system is configured to not reboot on panic, say the "panic_timeout" > > parameter equals 0, it will likely print out many noisy message like > > WARN() call stack for each and every CPU except the panic one, messages > > like below: > > > > Keeping the interrupt disabled will avoid the noisy message. > > > > When code runs to this point, it means user has chosed to not reboot, or > > do any special handling by using the panic notifier method, the only reason > > to enable the interrupt may be sysrq migic key and panic_blink function > > (though may not work even with irq enabled). > > > > So make the irq disabled by default and add a cmdline parameter > > "panic_keep_irq_on" to turn it on when needed. > > > > Signed-off-by: Feng Tang > > > > Acked-by: Steven Rostedt (VMware) I'm fine with the new boot param, but I think we need to leave it how it was by default: systems that want to see the blinking aren't going to have a screen to read about what boot param they need to add. Currently, we'll blink and spew extra warnings. With this patch we'll not blink and not spew: a headless machine will have no indication that a panic happened. -Kees -- Kees Cook
Re: [PATCH v4] panic: Avoid the extra noise dmesg
On Fri, 7 Dec 2018 17:51:19 +0800 Feng Tang wrote: > When kernel panic happens, it will first print the panic call stack, > then the ending msg like: > > [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception > [ 35.749975] [ cut here ] > > The above message are very useful for debugging. > > But if system is configured to not reboot on panic, say the "panic_timeout" > parameter equals 0, it will likely print out many noisy message like > WARN() call stack for each and every CPU except the panic one, messages > like below: > Keeping the interrupt disabled will avoid the noisy message. > > When code runs to this point, it means user has chosed to not reboot, or > do any special handling by using the panic notifier method, the only reason > to enable the interrupt may be sysrq migic key and panic_blink function > (though may not work even with irq enabled). > > So make the irq disabled by default and add a cmdline parameter > "panic_keep_irq_on" to turn it on when needed. > > Signed-off-by: Feng Tang > Acked-by: Steven Rostedt (VMware) -- Steve
[PATCH v4] panic: Avoid the extra noise dmesg
When kernel panic happens, it will first print the panic call stack,
then the ending msg like:
[ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception
[ 35.749975] [ cut here ]
The above message are very useful for debugging.
But if system is configured to not reboot on panic, say the "panic_timeout"
parameter equals 0, it will likely print out many noisy message like
WARN() call stack for each and every CPU except the panic one, messages
like below:
WARNING: CPU: 1 PID: 280 at kernel/sched/core.c:1198
set_task_cpu+0x183/0x190
Call Trace:
try_to_wake_up
default_wake_function
autoremove_wake_function
__wake_up_common
__wake_up_common_lock
__wake_up
wake_up_klogd_work_func
irq_work_run_list
irq_work_tick
update_process_times
tick_sched_timer
__hrtimer_run_queues
hrtimer_interrupt
smp_apic_timer_interrupt
apic_timer_interrupt
For people working in console mode, the screen will first show the panic
call stack, but immediately overridded by these noisy extra messages, which
makes debugging much more difficult, as the original context gets lost on
screen.
Also these noisy messages will confuse some users, as I have seen many bug
reporters posted the noisy message into bugzilla, instead of the real panic
call stack and context.
Keeping the interrupt disabled will avoid the noisy message.
When code runs to this point, it means user has chosed to not reboot, or
do any special handling by using the panic notifier method, the only reason
to enable the interrupt may be sysrq migic key and panic_blink function
(though may not work even with irq enabled).
So make the irq disabled by default and add a cmdline parameter
"panic_keep_irq_on" to turn it on when needed.
Signed-off-by: Feng Tang
Cc: Thomas Gleixner
Cc: Kees Cook
Cc: Borislav Petkov
Cc: Sergey Senozhatsky
Cc: Petr Mladek
Cc: Steven Rostedt
Cc: Andi Kleen
Cc: Peter Zijlstra
Cc: Sasha Levin
Cc: sta...@kernel.org
---
Changelog:
v4:
- make the local_irq_enable conditional and default off
to cover possible use of interrupt/scheduling, as
mentioned by Sergey and Petr
v3:
- Make the change log clearer as suggested by Andrew Morton
v2:
- Move the solution from hacking arch/scheduler code back
to panic.c
Documentation/admin-guide/kernel-parameters.txt | 6 ++
kernel/panic.c | 9 -
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index ad8dc61..45621e9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3093,6 +3093,12 @@
panic_on_warn panic() instead of WARN(). Useful to cause kdump
on a WARN().
+ panic_keep_irq_on
+ To keep the panic call stack info clean and suppress
+ noisy kernel message, the interrupt on panic cpu is
+ disabled by default. Add this to cmdline to enable
+ interrupt for panic cpu.
+
crash_kexec_post_notifiers
Run kdump after running panic-notifiers and dumping
kmsg. This only for the users who doubt kdump always
diff --git a/kernel/panic.c b/kernel/panic.c
index 85c4d14..04ace9b 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -40,6 +40,7 @@ static int pause_on_oops;
static int pause_on_oops_flag;
static DEFINE_SPINLOCK(pause_on_oops_lock);
bool crash_kexec_post_notifiers;
+bool panic_keep_irq_on;
int panic_on_warn __read_mostly;
int panic_timeout = CONFIG_PANIC_TIMEOUT;
@@ -322,7 +323,12 @@ void panic(const char *fmt, ...)
}
#endif
pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
- local_irq_enable();
+
+ if (panic_keep_irq_on)
+ local_irq_enable();
+ else
+ pr_emerg("Please add panic_keep_irq_on to cmdline if you want
blink/sysrq to work.");
+
for (i = 0; ; i += PANIC_TIMER_STEP) {
touch_softlockup_watchdog();
if (i >= i_next) {
@@ -684,6 +690,7 @@ core_param(panic, panic_timeout, int, 0644);
core_param(panic_print, panic_print, ulong, 0644);
core_param(pause_on_oops, pause_on_oops, int, 0644);
core_param(panic_on_warn, panic_on_warn, int, 0644);
+core_param(panic_keep_irq_on, panic_keep_irq_on, bool, 0644);
core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
static int __init oops_setup(char *s)
--
2.7.4
[PATCH v4] panic: Avoid the extra noise dmesg
When kernel panic happens, it will first print the panic call stack,
then the ending msg like:
[ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception
[ 35.749975] [ cut here ]
The above message are very useful for debugging.
But if system is configured to not reboot on panic, say the "panic_timeout"
parameter equals 0, it will likely print out many noisy message like
WARN() call stack for each and every CPU except the panic one, messages
like below:
WARNING: CPU: 1 PID: 280 at kernel/sched/core.c:1198
set_task_cpu+0x183/0x190
Call Trace:
try_to_wake_up
default_wake_function
autoremove_wake_function
__wake_up_common
__wake_up_common_lock
__wake_up
wake_up_klogd_work_func
irq_work_run_list
irq_work_tick
update_process_times
tick_sched_timer
__hrtimer_run_queues
hrtimer_interrupt
smp_apic_timer_interrupt
apic_timer_interrupt
For people working in console mode, the screen will first show the panic
call stack, but immediately overridded by these noisy extra messages, which
makes debugging much more difficult, as the original context gets lost on
screen.
Also these noisy messages will confuse some users, as I have seen many bug
reporters posted the noisy message into bugzilla, instead of the real panic
call stack and context.
Keeping the interrupt disabled will avoid the noisy message.
When code runs to this point, it means user has chosed to not reboot, or
do any special handling by using the panic notifier method, the only reason
to enable the interrupt may be sysrq migic key and panic_blink function
(though may not work even with irq enabled).
So make the irq disabled by default and add a cmdline parameter
"panic_keep_irq_on" to turn it on when needed.
Signed-off-by: Feng Tang
Cc: Thomas Gleixner
Cc: Kees Cook
Cc: Borislav Petkov
Cc: Sergey Senozhatsky
Cc: Petr Mladek
Cc: Steven Rostedt
Cc: Andi Kleen
Cc: Peter Zijlstra
Cc: Sasha Levin
Cc: sta...@kernel.org
---
Changelog:
v4:
- make the local_irq_enable conditional and default off
to cover possible use of interrupt/scheduling, as
mentioned by Sergey and Petr
v3:
- Make the change log clearer as suggested by Andrew Morton
v2:
- Move the solution from hacking arch/scheduler code back
to panic.c
Documentation/admin-guide/kernel-parameters.txt | 6 ++
kernel/panic.c | 9 -
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index ad8dc61..45621e9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3093,6 +3093,12 @@
panic_on_warn panic() instead of WARN(). Useful to cause kdump
on a WARN().
+ panic_keep_irq_on
+ To keep the panic call stack info clean and suppress
+ noisy kernel message, the interrupt on panic cpu is
+ disabled by default. Add this to cmdline to enable
+ interrupt for panic cpu.
+
crash_kexec_post_notifiers
Run kdump after running panic-notifiers and dumping
kmsg. This only for the users who doubt kdump always
diff --git a/kernel/panic.c b/kernel/panic.c
index 85c4d14..04ace9b 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -40,6 +40,7 @@ static int pause_on_oops;
static int pause_on_oops_flag;
static DEFINE_SPINLOCK(pause_on_oops_lock);
bool crash_kexec_post_notifiers;
+bool panic_keep_irq_on;
int panic_on_warn __read_mostly;
int panic_timeout = CONFIG_PANIC_TIMEOUT;
@@ -322,7 +323,12 @@ void panic(const char *fmt, ...)
}
#endif
pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
- local_irq_enable();
+
+ if (panic_keep_irq_on)
+ local_irq_enable();
+ else
+ pr_emerg("Please add panic_keep_irq_on to cmdline if you want
blink/sysrq to work.");
+
for (i = 0; ; i += PANIC_TIMER_STEP) {
touch_softlockup_watchdog();
if (i >= i_next) {
@@ -684,6 +690,7 @@ core_param(panic, panic_timeout, int, 0644);
core_param(panic_print, panic_print, ulong, 0644);
core_param(pause_on_oops, pause_on_oops, int, 0644);
core_param(panic_on_warn, panic_on_warn, int, 0644);
+core_param(panic_keep_irq_on, panic_keep_irq_on, bool, 0644);
core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
static int __init oops_setup(char *s)
--
2.7.4
