[CRIU] zdtm test build failure on s390x (s390x_regs_check.c)

[Adrian Reber]

On Wed, Sep 06, 2017 at 06:33:10PM +0200, Michael Holzheu wrote:
> On Wed, 6 Sep 2017 17:49:30 +0200
> Adrian Reber <adrian at lisas.de> wrote:
> 
> > On Tue, Sep 05, 2017 at 07:47:26PM +0200, Michael Holzheu wrote:
> > > On Tue, 5 Sep 2017 17:56:08 +0200
> > > Adrian Reber <adrian at lisas.de> wrote:
> > > 
> > > > When running 'make zdtm' on s390x it fails on my RHEL kernel with:
> > > > 
> > > > make[3]: Leaving directory `/tmp/criu/test/zdtm/lib'
> > > >  CC        s390x_regs_check.o
> > > > s390x_regs_check.c: In function ‘util_hexdump_grp’:
> > > > s390x_regs_check.c:214:7: error: ‘ptr’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> > > >    ptr += sprintf(ptr, "%02x", buf[i]);
> > > >        ^
> > > 
> > > Obviously the compiler does not understand the "if (first)" construct.
> > > 
> > > I assume the following will fix the problem:
> > > ---
> > > [CRIU][PATCH] zdtm/s390x_regs_check: Fix compiler warning
> > > 
> > > When running 'make zdtm' on s390x it fails on RHEL7 with:
> > > 
> > >  make[3]: Leaving directory `/tmp/criu/test/zdtm/lib'
> > >   CC        s390x_regs_check.o
> > >  s390x_regs_check.c: In function "util_hexdump_grp":
> > >  s390x_regs_check.c:214:7: error: "ptr" may be used uninitialized
> > >  in this function [-Werror=maybe-uninitialized]
> > >     ptr += sprintf(ptr, "%02x", buf[i]);
> > > 
> > > Fix this and assign ptr from the beginning to help gcc.
> > > 
> > > Signed-off-by: Michael Holzheu <holzheu at linux.vnet.ibm.com>
> > > ---
> > >  test/zdtm/static/s390x_regs_check.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/test/zdtm/static/s390x_regs_check.c b/test/zdtm/static/s390x_regs_check.c
> > > index a92679a..1a7e841 100644
> > > --- a/test/zdtm/static/s390x_regs_check.c
> > > +++ b/test/zdtm/static/s390x_regs_check.c
> > > @@ -198,8 +198,8 @@ struct reg_set *reg_set_vec[] = {
> > >  void util_hexdump_grp(const char *tag, const void *data, int grp,
> > >  		      int count, int indent)
> > >  {
> > > +	char str[1024], *ptr = str;
> > >  	const char *buf = data;
> > > -	char str[1024], *ptr;
> > >  	int i, first = 1;
> > >  
> > >  	for (i = 0; i < count; i++) {
> > > -- 
> > > 2.7.4
> > 
> > Thanks the patch works. Now it compiles without errors. But...
> > 
> > The test seems to hang. criu never starts in zdtm.py to do the actual
> > dump. In the output file I see:
> > 
> > 11:48:08.040: 45159: ------------- START 1 PROCESS + 2 THREADS ---------------
> > 11:48:08.080: 45159: STARTED: pid = 45160
> > 11:48:08.149: 45159: STARTED: pid = 45162
> > 11:48:08.149: 45159: STARTED: pid = 45161
> > 11:48:08.149: 45159: ---------------------- SET REGISTERS --------------------
> > 11:48:08.149: 45159: SET: pid = 45160
> > 11:48:08.174: 45159:  REGSET:      PRFPREG -> DONE
> > 11:48:08.174: 45159:  REGSET:     VXRS_LOW -> not supported by machine
> > 11:48:08.174: 45159:  REGSET:    VXRS_HIGH -> not supported by machine
> > 11:48:08.174: 45159: SET: pid = 45162
> 
> Looks like it started all threads and somehow hangs when attaching to
> the second thread with pid=45162 in ptrace_attach().
> 
> > 
> > One of the three process uses 100% CPU and that is how the process tree looks like:
> 
> After a thread is started it loops to ensure that it does not change
> registers any more:
> 
> static inline void send_tid_and_loop(int fd)
> {
>         int tid = syscall(__NR_gettid);
> 
>         asm volatile(
>                      "lgr       2,%0\n" /* Arg 1: fd */
>                      "la        3,%1\n" /* Arg 2: &tid */
>                      "lghi      4,4\n"  /* Arg 3: sizeof(int) */
>                      "svc       4\n"    /* __NR_write SVC: */
>                      /* After SVC no more registers are changed */
>                      "0:        j 0b\n" /* Loop here */
>                      : : "d" (fd), "Q" (tid) : "2", "3", "4");
> }
> 
> > 
> > 45166 pts/0    S+     0:00  |       \_ python2 ./zdtm.py run -f h,ns -t zdtm/static/s390x_regs_check
> > 45176 pts/0    S+     0:00  |           \_ ./zdtm_ct zdtm.py
> > 45179 pts/0    S+     0:00  |           |   \_ python2 zdtm.py
> > 45182 pts/0    S+     0:00  |           |       \_ python2 zdtm.py
> > 45199 pts/0    S+     0:00  |           |           \_ make --no-print-directory -C zdtm/static s390x_regs_check.pid
> > 45214 pts/0    S+     0:00  |           |               \_ ./s390x_regs_check --pidfile=s390x_regs_check.pid --outfile=s390x_regs_check.out
> > 45215 ?        Ss     0:00  |           |                   \_ ./s390x_regs_check --pidfile=s390x_regs_check.pid --outfile=s390x_regs_check.out
> > 45216 ?        Rl     0:16  |           |                       \_ ./s390x_regs_check --pidfile=s390x_regs_check.pid --outfile=s390x_regs_check.out
> > 45219 pts/0    R+     0:00  |           \_ ps axf
> 
> I probable will not be able to look into this the next two weeks.
> Alice will be back next week. I hope she can help you then.

The patch to fix the failing build is still not merged and the test
still hangs once your inlined patch is applied. Could you re-submit the
patch properly for Andrei to pick it up.

		Adrian