Re: [PATCH 5/7] i386, dumpstack: use x86_64's method to account die_nest_count

Neil Horman
2008-10-22T11:20:42Z

On Wed, Oct 22, 2008 at 12:00:12PM +0200, Alexander van Heukelum wrote:
> oops_begin/oops_end should always be used in pairs. On x86_64
> oops_begin increments die_nest_count, and oops_end decrements
> die_nest_count. Doing this makes oops_begin and oops_end equal
> to the x86_64 versions.
>
> Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>

Acked-by: Neil Horman <nhorman@tuxdriver.com>

> ---
> arch/x86/kernel/dumpstack_32.c | 29 +++++++++++++++++------------
> 1 files changed, 17 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
> index a29b88f..7c7d691 100644
> --- a/arch/x86/kernel/dumpstack_32.c
> +++ b/arch/x86/kernel/dumpstack_32.c
> @@ -289,21 +289,24 @@ static unsigned int die_nest_count;
>
> unsigned __kprobes long oops_begin(void)
> {
> + int cpu;
> unsigned long flags;
>
> oops_enter();
>
> - if (die_owner != raw_smp_processor_id()) {
> - console_verbose();
> - raw_local_irq_save(flags);
> - __raw_spin_lock(&die_lock);
> - die_owner = smp_processor_id();
> - die_nest_count = 0;
> - bust_spinlocks(1);
> - } else {
> - raw_local_irq_save(flags);
> + /* racy, but better than risking deadlock. */
> + raw_local_irq_save(flags);
> + cpu = smp_processor_id();
> + if (!__raw_spin_trylock(&die_lock)) {
> + if (cpu == die_owner)
> + /* nested oops. should stop eventually */;
> + else
> + __raw_spin_lock(&die_lock);
> }
> die_nest_count++;
> + die_owner = cpu;
> + console_verbose();
> + bust_spinlocks(1);
> return flags;
> }
>
> @@ -315,13 +318,15 @@ void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)
> bust_spinlocks(0);
> die_owner = -1;
> add_taint(TAINT_DIE);
> - __raw_spin_unlock(&die_lock);
> + die_nest_count--;
> + if (!die_nest_count)
> + /* Nest count reaches zero, release the lock. */
> + __raw_spin_unlock(&die_lock);
> raw_local_irq_restore(flags);
> -
> oops_exit();
> +
> if (!signr)
> return;
> -
> if (in_interrupt())
> panic("Fatal exception in interrupt");
> if (panic_on_oops)
> --
> 1.5.4.3
>
>

--
/****************************************************
* Neil Horman <nhorman@tuxdriver.com>
* Software Engineer, Red Hat
****************************************************/