Commit a4f18ed1 authored Jun 07, 2011 by Steven Rostedt Committed by Steven Rostedt Jun 07, 2011

ftrace: Revert 8ab2b7ef 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The original comment was outdated and stated that the interrupts were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>

parent 265a5b7e

kernel/trace/ftrace.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -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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