[PATCH 1/4] x86/stacktrace: return 0 instead of -1 for stack ops

[Steven Rostedt]

From: Steven Rostedt <srostedt@xxxxxxxxxx>

If we return -1 in the ops->stack for the stacktrace saving, we end up
breaking out of the loop if the stack we are tracing is in the exception
stack. This causes traces like:

          <idle>-0     [002] 34263.745825: raise_softirq_irqoff <-__blk_complete_request
          <idle>-0     [002] 34263.745826:
 <= 0
 <= 0
 <= 0
 <= 0
 <= 0
 <= 0
 <= 0

By returning "0" instead, the irq stack is saved as well, and we see:

          <idle>-0     [003]   883.280992: raise_softirq_irqoff <-__hrtimer_star
t_range_ns
          <idle>-0     [003]   883.280992:
 <= hrtimer_start_range_ns
 <= tick_nohz_restart_sched_tick
 <= cpu_idle
 <= start_secondary
 <=
 <= 0
 <= 0

[ Impact: record stacks from interrupts ]

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 arch/x86/kernel/stacktrace.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index f7bddc2..4aaf7e4 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -20,7 +20,7 @@ save_stack_warning_symbol(void *data, char *msg, unsigned long symbol)
 
 static int save_stack_stack(void *data, char *name)
 {
-	return -1;
+	return 0;
 }
 
 static void save_stack_address(void *data, unsigned long addr, int reliable)
-- 
1.6.2.4

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