ftrace/x86: One more missing sync after fixup of function modification failure
authorPetr Mladek <pmladek@suse.cz>
Mon, 24 Feb 2014 16:12:20 +0000 (17:12 +0100)
committerSteven Rostedt <rostedt@goodmis.org>
Tue, 4 Mar 2014 02:23:07 +0000 (21:23 -0500)
commit12729f14d8357fb845d75155228b21e76360272d
tree058f56b8a788e01366442bc9a942dc0ec08ac956
parentc932c6b7c913a5661e04059045fa1eac762c82fa
ftrace/x86: One more missing sync after fixup of function modification failure

If a failure occurs while modifying ftrace function, it bails out and will
remove the tracepoints to be back to what the code originally was.

There is missing the final sync run across the CPUs after the fix up is done
and before the ftrace int3 handler flag is reset.

Here's the description of the problem:

CPU0 CPU1
---- ----
  remove_breakpoint();
  modifying_ftrace_code = 0;

[still sees breakpoint]
<takes trap>
[sees modifying_ftrace_code as zero]
[no breakpoint handler]
[goto failed case]
[trap exception - kernel breakpoint, no
 handler]
BUG()

Link: http://lkml.kernel.org/r/1393258342-29978-2-git-send-email-pmladek@suse.cz
Fixes: 8a4d0a687a5 "ftrace: Use breakpoint method to update ftrace caller"
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.cz>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
arch/x86/kernel/ftrace.c