From a4f18ed11a4ddf327dd91cd19e237278600ad327 Mon Sep 17 00:00:00 2001
From: Steven Rostedt <srostedt@redhat.com>
Date: Tue, 7 Jun 2011 09:26:46 -0400
Subject: [PATCH] ftrace: Revert 8ab2b7efd ftrace: Remove unnecessary disabling
of irqs
Revert the commit that removed the disabling of interrupts around
the initial modifying of mcount callers to nops, and update the comment.
The original comment was outdated and stated that the interrupts were
being disabled to prevent kstop machine, which was required with the
old ftrace daemon, but was no longer the case.
What the comment failed to mention was that interrupts needed to be
disabled to keep interrupts from preempting the modifying of the code
and then executing the code that was partially modified.
Revert the commit and update the comment.
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/ftrace.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 204b3eb4e690..908038f57440 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3330,6 +3330,7 @@ static int ftrace_process_locs(struct module *mod,
{
unsigned long *p;
unsigned long addr;
+ unsigned long flags;
mutex_lock(&ftrace_lock);
p = start;
@@ -3346,7 +3347,13 @@ static int ftrace_process_locs(struct module *mod,
ftrace_record_ip(addr);
}
+ /*
+ * Disable interrupts to prevent interrupts from executing
+ * code that is being modified.
+ */
+ local_irq_save(flags);
ftrace_update_code(mod);
+ local_irq_restore(flags);
mutex_unlock(&ftrace_lock);
return 0;
--
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