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SubjectRe: [for-next][PATCH 10/31] scripts: ftrace - move the sort-processing in ftrace_init
On Sat, 15 Jan 2022 13:36:04 -0700
Nathan Chancellor <nathan@kernel.org> wrote:

> Hi Steven and Yinan,
>
> On Tue, Jan 11, 2022 at 12:30:41PM -0500, Steven Rostedt wrote:
> > From: Yinan Liu <yinan@linux.alibaba.com>
> >
> > When the kernel starts, the initialization of ftrace takes
> > up a portion of the time (approximately 6~8ms) to sort mcount
> > addresses. We can save this time by moving mcount-sorting to
> > compile time.
> >
> > Link: https://lkml.kernel.org/r/20211212113358.34208-2-yinan@linux.alibaba.com
> >
> > Signed-off-by: Yinan Liu <yinan@linux.alibaba.com>
> > Reported-by: kernel test robot <lkp@intel.com>
> > Reported-by: kernel test robot <oliver.sang@intel.com>
> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
>
> This change as commit 72b3942a173c ("scripts: ftrace - move the
> sort-processing in ftrace_init") in -next causes a bunch of warnings at
> the beginning of the build when using clang as the host compiler:
>


>
> Should mcount_sort_thread be zero initialized or is there something else
> going on here? I am currently hunting down a bunch of other regressions
> so apologies for just the report rather than a patch to fix it.

Can this really happen? We have:

if (pthread_create(&mcount_sort_thread, NULL, &sort_mcount_loc, &mstruct)) {
fprintf(stderr,
"pthread_create mcount_sort_thread failed '%s': %s\n",
strerror(errno), fname);
goto out;
}
[..]

if (mcount_sort_thread) {
void *retval = NULL;
/* wait for mcount sort done */
rc = pthread_join(mcount_sort_thread, &retval);
if (rc) {
fprintf(stderr,
"pthread_join failed '%s': %s\n",
strerror(errno), fname);
} else if (retval) {
rc = -1;
fprintf(stderr,
"failed to sort mcount '%s': %s\n",
(char *)retval, fname);
}
}

Shouldn't the pthread_create() initialize it? And I'm not even sure if we
need that if statement?

Or is there a path to get there without pthread_create() initializing it?

-- Steve

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