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Message-ID: <BANLkTi=ZrPkRwFSmdkAB60-MKS3fwZOjpg@mail.gmail.com>
Date: Thu, 26 May 2011 19:38:19 +0200
From: richard -rw- weinberger <richard.weinberger@...il.com>
To: prasad@...ux.vnet.ibm.com
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Andi Kleen <andi@...stfloor.org>,
"Luck, Tony" <tony.luck@...el.com>,
Vivek Goyal <vgoyal@...hat.com>, kexec@...ts.infradead.org,
"Eric W. Biederman" <ebiederm@...ssion.com>, anderson@...hat.com
Subject: Re: [Patch 1/6] XPANIC: Add extended panic interface
On Thu, May 26, 2011 at 7:12 PM, K.Prasad <prasad@...ux.vnet.ibm.com> wrote:
>
> commit e668fa1aea7844ac4c7ea09030a2f3e647a4adb1
> Author: Andi Kleen <ak@...ux.intel.com>
> Date: Fri Nov 19 18:36:44 2010 +0100
>
> XPANIC: Add extended panic interface
>
> One panic size doesn't fit all.
>
> Machine check has some special requirements on panic, like:
> - It wants to do a reboot timeout by default so that the machine
> check event can be logged to disk after warm reboot.
> - For memory errors it usually doesn't want to do crash dumps because
> that can lead to crash loops (dumping corrupted memory would
> lead to another machine check)
> - It doesn't want to do backtraces because machine checks
> are not a kernel bug.
>
> In a earlier patch this was done with various adhoc hacks,
> but it's cleaner to extend panic to a 'xpanic' that directly
> gets a flag and timeout argument.
>
> The only user right now will be x86 machine checks, but I consider
> it likely that other users will switch to this too.
>
> For example one obvious candidate would be the "no root
> found" panic which doesn't really deserve a backtrace.
>
> I exported a vpanic() interface too as a global. That's not
> needed by the current user, but the interface has to exist
> internally anyways and I could see how other code would
> find a v* variant of panic useful.
>
> Originally based on a suggestion by H. Peter Anvin.
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
>
> ---
> include/linux/kernel.h | 11 +++++++++++
> kernel/panic.c | 41 +++++++++++++++++++++++++++++++----------
> 2 files changed, 42 insertions(+), 10 deletions(-)
>
> Index: linux-2.6.slim_kdump/include/linux/kernel.h
> ===================================================================
> --- linux-2.6.slim_kdump.orig/include/linux/kernel.h
> +++ linux-2.6.slim_kdump/include/linux/kernel.h
> @@ -175,10 +175,21 @@ static inline void might_fault(void)
> }
> #endif
>
> +enum panic_flags {
> + PANIC_NO_KEXEC = (1 << 0),
> + PANIC_NO_BACKTRACE = (1 << 1),
> +};
> +
> extern struct atomic_notifier_head panic_notifier_list;
> extern long (*panic_blink)(int state);
> NORET_TYPE void panic(const char * fmt, ...)
> __attribute__ ((NORET_AND format (printf, 1, 2))) __cold;
> +NORET_TYPE void xpanic(enum panic_flags flags, int timeout,
> + const char *fmt, ...)
> + __attribute__ ((NORET_AND format (printf, 3, 4))) __cold;
> +NORET_TYPE void vpanic(enum panic_flags flags, int timeout,
> + const char *fmt,
> + va_list ap) __noreturn __cold;
> extern void oops_enter(void);
> extern void oops_exit(void);
> void print_oops_end_marker(void);
> Index: linux-2.6.slim_kdump/kernel/panic.c
> ===================================================================
> --- linux-2.6.slim_kdump.orig/kernel/panic.c
> +++ linux-2.6.slim_kdump/kernel/panic.c
> @@ -57,14 +57,37 @@ EXPORT_SYMBOL(panic_blink);
> *
> * This function never returns.
> */
> -NORET_TYPE void panic(const char * fmt, ...)
> +NORET_TYPE void panic(const char *fmt, ...)
> +{
> + va_list ap;
> + va_start(ap, fmt);
> + vpanic(0, 0, fmt, ap);
> +}
> +EXPORT_SYMBOL(panic);
> +
> +NORET_TYPE void xpanic(enum panic_flags flags, int timeout,
> + const char *fmt, ...)
> +{
> + va_list ap;
> + va_start(ap, fmt);
> + xpanic(flags, timeout, fmt, ap);
Why are you calling xpanic() here again?
I guess you meant vpanic().
> +}
> +EXPORT_SYMBOL(xpanic);
> +
> +NORET_TYPE void vpanic(enum panic_flags flags, int timeout,
> + const char * fmt, va_list args)
> {
> static char buf[1024];
> - va_list args;
> long i, i_next = 0;
> int state = 0;
>
> /*
> + * Let user always override panic_timeout.
> + */
> + if (panic_timeout > 0)
> + timeout = panic_timeout;
> +
> + /*
> * It's possible to come here directly from a panic-assertion and
> * not have preempt disabled. Some functions called from here want
> * preempt to be disabled. No point enabling it later though...
> @@ -73,12 +96,11 @@ NORET_TYPE void panic(const char * fmt,
>
> console_verbose();
> bust_spinlocks(1);
> - va_start(args, fmt);
> vsnprintf(buf, sizeof(buf), fmt, args);
> - va_end(args);
> printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
> #ifdef CONFIG_DEBUG_BUGVERBOSE
> - dump_stack();
> + if (!(flags & PANIC_NO_BACKTRACE))
> + dump_stack();
> #endif
>
> /*
> @@ -86,7 +108,8 @@ NORET_TYPE void panic(const char * fmt,
> * everything else.
> * Do we want to call this before we try to display a message?
> */
> - crash_kexec(NULL);
> + if (!(flags & PANIC_NO_KEXEC))
> + crash_kexec(NULL);
>
> kmsg_dump(KMSG_DUMP_PANIC);
>
> @@ -104,7 +127,7 @@ NORET_TYPE void panic(const char * fmt,
> if (!panic_blink)
> panic_blink = no_blink;
>
> - if (panic_timeout > 0) {
> + if (timeout > 0) {
> /*
> * Delay timeout seconds before rebooting the machine.
> * We can't use the "normal" timers since we just panicked.
> @@ -152,9 +175,7 @@ NORET_TYPE void panic(const char * fmt,
> mdelay(PANIC_TIMER_STEP);
> }
> }
> -
> -EXPORT_SYMBOL(panic);
> -
> +EXPORT_SYMBOL(vpanic);
>
> struct tnt {
> u8 bit;
> --
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--
Thanks,
//richard
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