Messages in this thread | | | Date | Thu, 11 Oct 2012 14:18:45 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] panic: fix incomplete panic log in panic() |
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On Thu, 11 Oct 2012 16:03:07 +0800 Qing Zhu <qzhu@marvell.com> wrote:
> Panic log should be printed on the console, but if someone lock the > console when panic, console won't print out panic log. > > The incomplete panic log issue will happen in below scenarios: > 1. One task call console_lock(), then panic happend before it call > console_unlock(). No panic log can be printed. > 2. Cpu 0 call panic()->Cpu 1 call console_lock()->Cpu 0 call > smp_send_stop() > Cpu 1 will be stopped and can't unlock console,only top part of panic log > will be printed. > > So unlock console anyway in panic() to keep panic log printed. > > Signed-off-by: Qing Zhu <qzhu@marvell.com> > --- > kernel/panic.c | 8 ++++++++ > 1 files changed, 8 insertions(+), 0 deletions(-) > > diff --git a/kernel/panic.c b/kernel/panic.c > index e1b2822..3924d25 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -23,6 +23,7 @@ > #include <linux/init.h> > #include <linux/nmi.h> > #include <linux/dmi.h> > +#include <linux/console.h> > > #define PANIC_TIMER_STEP 100 > #define PANIC_BLINK_SPD 18 > @@ -127,6 +128,13 @@ void panic(const char *fmt, ...) > > atomic_notifier_call_chain(&panic_notifier_list, 0, buf); > > + /* > + * Unlock the console anyway here, in case it's occupied by another > + * one which has no chance to unlock the console thus prevents the > + * panic log prints on the console. > + */ > + console_unlock(); > + > bust_spinlocks(0); > > if (!panic_blink)
hm. console_unlock() does a large amount of work, and it seems risky to do all of that when the system is in a bad-and-getting-worse state.
Is there some more modest thing we could do here, for example,
if (console_locked) { up(&console_sem); console_locked = 0; }
or something along those lines?
Also, perhaps this operation should be moved into bust_spinlocks(). What would have happened if your code had triggered an oops, rather than called panic()?
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