Re: [PATCH] MIPS: lib: Mark intrinsics notrace

[Harvey Hunt]

Hi Ralf,

On 29/05/16 22:03, Ralf Baechle wrote:
> On Wed, May 25, 2016 at 11:06:35AM +0100, Harvey Hunt wrote:
>
> > On certain MIPS32 devices, the ftrace tracer "function_graph" uses
> > __lshrdi3() during the capturing of trace data. ftrace then attempts to
> > trace __lshrdi3() which leads to infinite recursion and a stack overflow.
> > Fix this by marking __lshrdi3() as notrace. Mark the other compiler
> > intrinsics as notrace in case the compiler decides to use them in the
> > ftrace path.
>
> Makes perfect sense - but I'm wondering how you triggered it.  Was this
> a build with the GCC option -Os that is CONFIG_CC_OPTIMIZE_FOR_SIZE?
> Usually people build with CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE that is -O2
> which results in intrinsics being inlined.

This is triggered by building with CONFIG_CC_OPTIMIZE_FOR_SIZE. This 
explains why I only saw it on certain MIPS32 devices - Malta's 
defconfigs don't have CONFIG_CC_OPTIMIZE_FOR_SIZE enabled, but the 
pistachio and Ci20 defconfigs do.

>   Ralf

Thanks,

Harvey