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authorSteven Rostedt <srostedt@redhat.com>2011-06-07 09:26:46 -0400
committerSteven Rostedt <rostedt@goodmis.org>2011-06-07 14:49:19 -0400
commita4f18ed11a4ddf327dd91cd19e237278600ad327 (patch)
treebbe96241c6db2be16e881920a3312ec937ed7cd1 /kernel/trace
parent265a5b7ee3eb21a4d0e53e17d59ba6eada91af39 (diff)
downloadlwn-a4f18ed11a4ddf327dd91cd19e237278600ad327.tar.gz
lwn-a4f18ed11a4ddf327dd91cd19e237278600ad327.zip
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 The original comment was outdated and stated that the interrupts were being disabled to prevent kstop machine, which was required with the old ftrace daemon, but was no longer the case.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>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/ftrace.c7
1 files changed, 7 insertions, 0 deletions
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;