Re: Linux 5.5=rc1 kselftest rseq test build failure

From: Shuah Khan
Date: Wed Dec 11 2019 - 10:45:53 EST

On 12/11/19 8:19 AM, Mathieu Desnoyers wrote:
----- On Dec 10, 2019, at 7:27 PM, Shuah Khan skhan@xxxxxxxxxxxxxxxxxxx wrote:

Hi Mathieu,

I am seeing rseq test build failure on Linux 5.5-rc1.

gcc -O2 -Wall -g -I./ -I../../../../usr/include/ -L./ -Wl,-rpath=./
param_test.c -lpthread -lrseq -o
param_test.c:18:21: error: static declaration of âgettidâ follows
non-static declaration
18 | static inline pid_t gettid(void)
| ^~~~~~
In file included from /usr/include/unistd.h:1170,
from param_test.c:11:
/usr/include/x86_64-linux-gnu/bits/unistd_ext.h:34:16: note: previous
declaration of âgettidâ was here
34 | extern __pid_t gettid (void) __THROW;
| ^~~~~~
make: *** [Makefile:28:] Error 1

The following obvious change fixes it. However, there could be reason
why this was defined here. If you think this is the right fix, I can
send the patch. I started seeing this with gcc version 9.2.1 20191008

This issue is caused by introduction of "gettid()" in glibc 2.30. I don't
think we want to introduce a build dependency on glibc 2.30 for kernel
selftests. Removing the gettid() symbol as you propose here will break
build environments with glibc < 2.30.

We could eventually try to figure out whether the glibc headers implement
gettid() at build time (not sure how), or we could simply rename our own
"gettid()" to "rseq_gettid()", thus removing the namespace clash with

I can propose a patch renaming gettid() to rseq_gettid() is that approach
is OK with you.

Looks like you already have a patch to do this. I see it in my Inbox.
I could take that.

-- Shuah