tile: avoid recursive backtrace faults
This change adds support for avoiding recursive backtracer crashes;
we haven't seen this in practice other than when things are seriously
corrupt, but it may help avoid losing the root cause of a crash.
Also, don't abort kernel backtracers for invalid userspace PC's.
If we do, we lose the ability to backtrace through a userspace
call to a bad address above PAGE_OFFSET, even though that it can
be perfectly reasonable to continue the backtrace in such a case.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
diff --git a/arch/tile/include/asm/processor.h b/arch/tile/include/asm/processor.h
index cda2724..fed1c04 100644
--- a/arch/tile/include/asm/processor.h
+++ b/arch/tile/include/asm/processor.h
@@ -110,6 +110,8 @@
unsigned long long interrupt_mask;
/* User interrupt-control 0 state */
unsigned long intctrl_0;
+ /* Is this task currently doing a backtrace? */
+ bool in_backtrace;
#if CHIP_HAS_PROC_STATUS_SPR()
/* Any other miscellaneous processor state bits */
unsigned long proc_status;