Re: [PATCH 3/3] ftrace: Revert 8ab2b7efd ftrace: Remove unnecessarydisabling of
From: Richard W.M. Jones
Date: Tue Jun 07 2011 - 13:20:56 EST
On Tue, Jun 07, 2011 at 01:07:43PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <srostedt@xxxxxxxxxx>
> 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 The original comment was outdated and stated that the interrupts were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 commint and update the comment.
> Reported-by: Richard W.M. Jones <rjones@xxxxxxxxxx>
> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> kernel/trace/ftrace.c | 7 +++++++
> 1 files changed, 7 insertions(+), 0 deletions(-)
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 204b3eb..908038f 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;
> p = start;
> @@ -3346,7 +3347,13 @@ static int ftrace_process_locs(struct module *mod,
> + /*
> + * Disable interrupts to prevent interrupts from executing
> + * code that is being modified.
> + */
> + local_irq_save(flags);
> + local_irq_restore(flags);
> return 0;
I have extensively tested this patch because it was required in order
to fix a boot problem with libguestfs on Fedora Rawhide:
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-top is 'top' for virtual machines. Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/