* James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > On Wed, 2012-07-25 at 09:45 +0200, Ingo Molnar wrote: > > * Tony Luck <tony.luck@xxxxxxxxx> wrote: > > > > > The stack_not_used() function in <linux/sched.h> assumes that stacks > > > grow downwards. This is not true on IA64 or PARISC, so this function > > > would walk off in the wrong direction and into the weeds. > > > > > > Found on IA64 because of a compilation failure with recursive dependencies > > > on IA64_TASKSIZE and IA64_THREAD_INFO_SIZE. > > > > > > Fixing the code is possible, but should be combined with other > > > infrastructure additions to set up the "canary" at the end of the stack. > > > > > > Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx> (failed allmodconfig build) > > > Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx> > > > --- > > > lib/Kconfig.debug | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > > index ff5bdee..4a18650 100644 > > > --- a/lib/Kconfig.debug > > > +++ b/lib/Kconfig.debug > > > @@ -714,7 +714,7 @@ config STACKTRACE > > > > > > config DEBUG_STACK_USAGE > > > bool "Stack utilization instrumentation" > > > - depends on DEBUG_KERNEL > > > + depends on DEBUG_KERNEL && !IA64 && !PARISC > > > > The modern way of doing this is by adding an ARCH_SUPPORTS_ > > flag. > > That's a bit daft, isn't it? [...] It's generally more maintainable than a random list of architecture exclusions because every (old or new) architecture can just grep for ARCH_SUPPORTS_ pattern and see whether they support everything that others support. The above exclusion list of architectures is much harder to find in a structured way. > [...] We'd have to add ARCH_SUPPORTS_ flags to about 25 > separate architectures just to get it not supported on these > two. That is one off overhead and it makes things easier to maintain going forward. Anyway, that's the current upstream technique and it's been in place for years. > Since the problem is an invalid assumption about how the stack > grows, why not just condition it on that. We actually have a > config option for this: CONFIG_STACK_GROWSUP. But for some > reason ia64 doesn't define this, why not, Tony? It looks > deliberate because you have replaced a lot of > > #ifdef CONFIG_STACK_GROWSUP > > with > > #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64) > > but not all of them. Yes, that's another possible solution, assuming that it's really only about the up/down difference. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|