On Thu, 3 Nov 2016 14:58:38 +0100
Heiko Carstens <heiko.carst...@de.ibm.com> wrote:
> Commit 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like
> events do") added a couple of this_cpu_read calls to the ftrace code.
>
> On x86 this is not a problem, since it has single instructions to read
> percpu data. Other architectures which use the generic variant now
> have additional preempt_disable and preempt_enable calls in the core
> ftrace code. This may lead to recursive calls and in result to a dead
> machine, e.g. if preemption and debugging options are enabled.
>
> To fix this use the notrace variant of preempt_disable and
> preempt_enable within the generic percpu code.
>
> Reported-and-bisected-by: Sebastian Ott <seb...@linux.vnet.ibm.com>
> Tested-by: Sebastian Ott <seb...@linux.vnet.ibm.com>
> Fixes: 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like events
> do")
> Signed-off-by: Heiko Carstens <heiko.carst...@de.ibm.com>
Acked-by: Steven Rostedt <rost...@goodmis.org>
Feel free to push this in your tree.
-- Steve
> ---
> include/asm-generic/percpu.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
> index 40e887068da2..0504ef8f3aa3 100644
> --- a/include/asm-generic/percpu.h
> +++ b/include/asm-generic/percpu.h
> @@ -118,9 +118,9 @@ do {
> \
> #define this_cpu_generic_read(pcp) \
> ({ \
> typeof(pcp) __ret; \
> - preempt_disable(); \
> + preempt_disable_notrace(); \
> __ret = raw_cpu_generic_read(pcp); \
> - preempt_enable(); \
> + preempt_enable_notrace(); \
> __ret; \
> })
>
