Messages in this thread | | | Date | Mon, 21 Apr 2014 08:30:32 -0400 | From | Vivek Goyal <> | Subject | Re: [PATCH v3] kernel/panic: Add "crash_kexec_post_notifiers" option for kdump after panic_notifers |
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On Mon, Apr 21, 2014 at 10:33:48AM +0900, Masami Hiramatsu wrote: > Add a "crash_kexec_post_notifiers" option to run kdump after running > panic_notifiers and dump kmsg. This can help rare situations which > kdump drops in failure because of unstable crashed kernel or hardware > failure (memory corruption on critical data/code), or the 2nd kernel > is already broken by the 1st kernel (it's a broken behavior, but who > can guarantee that the "crashed" kernel works correctly?). > > Usage: add "crash_kexec_post_notifiers" to kernel boot option. > > Note that this actually increases risks of the failure of kdump. > This option should be set only if you worry about the rare case > of kdump failure rather than increasing the chance of success. > > Changes from v2: > - Remove warning message according to Vivek's comment. > > Changes from v1: > - Rename late_kdump option to crash_kexec_post_notifiers. > - Remove unneeded warning message. > > Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> > Acked-by: Motohiro Kosaki <Motohiro.Kosaki@us.fujitsu.com> > Cc: Eric Biederman <ebiederm@xmission.com> > Cc: Vivek Goyal <vgoyal@redhat.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com> > Cc: Satoru MORIYA <satoru.moriya.br@hitachi.com> > Cc: Tomoki Sekiyama <tomoki.sekiyama@hds.com> > --- > Documentation/kernel-parameters.txt | 8 ++++++++ > kernel/panic.c | 23 +++++++++++++++++++++-- > 2 files changed, 29 insertions(+), 2 deletions(-)
I think let us do it. Quite a few people have been asking for allowing to run hook for saving kernel buffers to NVRAM before we transition into kdump kernel.
I understand that it opens flood gate for every kind of hook to be executed but that's the not default and if user decides to set crash_kexec_post_notifiers, they understand that they are increasing the chances of kdump failures.
If they decide to do that, they need to live with this trade-off.
We have pushed back on this for a very long time. I guess it is time to give it a chance and see how does it go. Does it really help those who want to do run notifiers before kdump kicks in.
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Thanks Vivek
> > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index 03e50b4..1df416b 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2339,6 +2339,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > timeout < 0: reboot immediately > Format: <timeout> > > + crash_kexec_post_notifiers > + Run kdump after running panic-notifiers and dumping > + kmsg. This only for the users who doubt kdump always > + succeeds in any situation. > + Note that this also increases risks of kdump failure, > + because some panic notifiers can make the crashed > + kernel more unstable. > + > parkbd.port= [HW] Parallel port number the keyboard adapter is > connected to, default is 0. > Format: <parport#> > diff --git a/kernel/panic.c b/kernel/panic.c > index d02fa9f..30c4a1c 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -32,6 +32,7 @@ static unsigned long tainted_mask; > static int pause_on_oops; > static int pause_on_oops_flag; > static DEFINE_SPINLOCK(pause_on_oops_lock); > +static bool crash_kexec_post_notifiers; > > int panic_timeout = CONFIG_PANIC_TIMEOUT; > EXPORT_SYMBOL_GPL(panic_timeout); > @@ -112,9 +113,11 @@ void panic(const char *fmt, ...) > /* > * If we have crashed and we have a crash kernel loaded let it handle > * everything else. > - * Do we want to call this before we try to display a message? > + * If we want to run this after calling panic_notifiers, pass > + * the "crash_kexec_post_notifiers" option to the kernel. > */ > - crash_kexec(NULL); > + if (!crash_kexec_post_notifiers) > + crash_kexec(NULL); > > /* > * Note smp_send_stop is the usual smp shutdown function, which > @@ -131,6 +134,15 @@ void panic(const char *fmt, ...) > > kmsg_dump(KMSG_DUMP_PANIC); > > + /* > + * If you doubt kdump always works fine in any situation, > + * "crash_kexec_post_notifiers" offers you a chance to run > + * panic_notifiers and dumping kmsg before kdump. > + * Note: since some panic_notifiers can make crashed kernel > + * more unstable, it can increase risks of the kdump failure too. > + */ > + crash_kexec(NULL); > + > bust_spinlocks(0); > > if (!panic_blink) > @@ -472,6 +484,13 @@ EXPORT_SYMBOL(__stack_chk_fail); > core_param(panic, panic_timeout, int, 0644); > core_param(pause_on_oops, pause_on_oops, int, 0644); > > +static int __init setup_crash_kexec_post_notifiers(char *s) > +{ > + crash_kexec_post_notifiers = true; > + return 0; > +} > +early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers); > + > static int __init oops_setup(char *s) > { > if (!s) >
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