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Subject[PATCH 2/2] Some stacks show up untracable, so fall back to old method in this case
Date
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
---
arch/x86_64/kernel/stacktrace.c | 10 ++++++++--
include/linux/stacktrace.h | 1 +
kernel/latency_trace.c | 12 ++++++++++++
3 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/arch/x86_64/kernel/stacktrace.c b/arch/x86_64/kernel/stacktrace.c
index cb91091..054f627 100644
--- a/arch/x86_64/kernel/stacktrace.c
+++ b/arch/x86_64/kernel/stacktrace.c
@@ -24,7 +24,7 @@ static int save_stack_stack(void *data, char *name)
return -1;
}

-static void save_stack_address(void *data, unsigned long addr)
+static void _save_stack_address(void *data, unsigned long addr)
{
struct stack_trace *trace = (struct stack_trace *)data;
if (trace->skip > 0) {
@@ -39,7 +39,7 @@ static struct stacktrace_ops save_stack_ops = {
.warning = save_stack_warning,
.warning_symbol = save_stack_warning_symbol,
.stack = save_stack_stack,
- .address = save_stack_address,
+ .address = _save_stack_address,
};

/*
@@ -52,3 +52,9 @@ void save_stack_trace(struct stack_trace *trace)
trace->entries[trace->nr_entries++] = ULONG_MAX;
}
EXPORT_SYMBOL(save_stack_trace);
+
+void save_stack_address(struct stack_trace *trace, unsigned long addr)
+{
+ _save_stack_address(trace, addr);
+}
+EXPORT_SYMBOL(save_stack_address);
diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index e7fa657..5acad27 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h
@@ -9,6 +9,7 @@ struct stack_trace {
};

extern void save_stack_trace(struct stack_trace *trace);
+extern void save_stack_address(struct stack_trace *trace, unsigned long addr);

extern void print_stack_trace(struct stack_trace *trace, int spaces);
#else
diff --git a/kernel/latency_trace.c b/kernel/latency_trace.c
index 9b83262..82c04ac 100644
--- a/kernel/latency_trace.c
+++ b/kernel/latency_trace.c
@@ -2058,6 +2058,18 @@ void notrace add_preempt_count(unsigned int val)
trace->entries = current->preempt_trace[idx].data;

save_stack_trace(trace);
+
+ /*
+ * If we couldnt get our trace, the first entry will
+ * have the ULONG_MAX marker. In that case, we
+ * rewind and save our simple two level stack
+ */
+ if ((trace->nr_entries == 1)
+ && (trace->entries[0] == ULONG_MAX)) {
+ trace->nr_entries = 0;
+ save_stack_address(trace, eip);
+ save_stack_address(trace, parent_eip);
+ }
}
}
#endif
-
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