[PATCH v2 07/14] elf: Add test case for [BZ #19329]

[Adhemerval Zanella]

On 13/04/2021 05:19, Szabolcs Nagy via Libc-alpha wrote:
> Test concurrent dlopen and pthread_create when the loaded modules have
> TLS.  This triggers dl-tls assertion failures more reliably than the
> nptl/tst-stack4 test.
> 
> The dlopened module has 100 DT_NEEDED dependencies with TLS, they were
> reused from an existing TLS test. The number of created threads during
> dlopen depends on filesystem speed and hardware, but at most 3 threads
> are alive at a time to limit resource usage.
> 
> ---
> v5:
> - moved from nptl/ to elf/
> - use many tls modules from another test (affects the timing a bit as
>   these need more relocation processing, but still detects the race)
> - use xdlopen
> - use stdatomic.h
> - moved from tests-internal back to tests
> - use acq/rel atomics instead of relaxed, this works too and cleaner.
> - moved after bug fix patch.
> 
> v4:
> - rebased, updated copyright year.
> - moved to tests-internal because of <atomic.h>
> 
> v3:
> - use the new test support code.
> - better Makefile usage so modules are cleaned properly.
> 
> v2:
> - undef NDEBUG.
> - join nop threads so at most 3 threads exist at a time.
> - remove stack size setting (resource usage is no longer a concern).
> - stop creating threads after dlopen observably finished.
> - print the number of threads created for debugging.

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  elf/Makefile       |  9 ++++--
>  elf/tst-tls21.c    | 68 ++++++++++++++++++++++++++++++++++++++++++++++
>  elf/tst-tls21mod.c |  1 +
>  3 files changed, 76 insertions(+), 2 deletions(-)
>  create mode 100644 elf/tst-tls21.c
>  create mode 100644 elf/tst-tls21mod.c
> 
> diff --git a/elf/Makefile b/elf/Makefile
> index b1344f1133..e9377608eb 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -223,7 +223,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
>  	 tst-single_threaded tst-single_threaded-pthread \
>  	 tst-tls-ie tst-tls-ie-dlmopen argv0test \
>  	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
> -	 tst-tls20
> +	 tst-tls20 tst-tls21
>  #	 reldep9
>  tests-internal += loadtest unload unload2 circleload1 \
>  	 neededtest neededtest2 neededtest3 neededtest4 \

Ok.

> @@ -345,7 +345,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
>  		libmarkermod2-1 libmarkermod2-2 \
>  		libmarkermod3-1 libmarkermod3-2 libmarkermod3-3 \
>  		libmarkermod4-1 libmarkermod4-2 libmarkermod4-3 libmarkermod4-4 \
> -		tst-tls20mod-bad
> +		tst-tls20mod-bad tst-tls21mod
>  
>  # Most modules build with _ISOMAC defined, but those filtered out
>  # depend on internal headers.

Ok.

> @@ -1932,3 +1932,8 @@ tst-tls20mod-bad.so-no-z-defs = yes
>  $(objpfx)tst-tls20: $(libdl) $(shared-thread-library)
>  $(objpfx)tst-tls20.out: $(objpfx)tst-tls20mod-bad.so \
>  			$(tst-tls-many-dynamic-modules:%=$(objpfx)%.so)
> +
> +# Reuses tst-tls-many-dynamic-modules
> +$(objpfx)tst-tls21: $(libdl) $(shared-thread-library)
> +$(objpfx)tst-tls21.out: $(objpfx)tst-tls21mod.so
> +$(objpfx)tst-tls21mod.so: $(tst-tls-many-dynamic-modules:%=$(objpfx)%.so)

Ok.

> diff --git a/elf/tst-tls21.c b/elf/tst-tls21.c
> new file mode 100644
> index 0000000000..560bf5813a
> --- /dev/null
> +++ b/elf/tst-tls21.c
> @@ -0,0 +1,68 @@
> +/* Test concurrent dlopen and pthread_create: BZ 19329.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <dlfcn.h>
> +#include <pthread.h>
> +#include <stdio.h>
> +#include <stdatomic.h>
> +#include <support/xdlfcn.h>
> +#include <support/xthread.h>
> +
> +#define THREADS 10000
> +
> +static atomic_int done;
> +
> +static void *
> +start (void *a)
> +{
> +  /* Load a module with many dependencies that each have TLS.  */
> +  xdlopen ("tst-tls21mod.so", RTLD_LAZY);
> +  atomic_store_explicit (&done, 1, memory_order_release);
> +  return 0;
> +}
> +
> +static void *
> +nop (void *a)
> +{
> +  return 0;
> +}
> +
> +static int
> +do_test (void)
> +{
> +  pthread_t t1, t2;
> +  int i;
> +
> +  /* Load a module with lots of dependencies and TLS.  */
> +  t1 = xpthread_create (0, start, 0);
> +
> +  /* Concurrently create lots of threads until dlopen is observably done.  */
> +  for (i = 0; i < THREADS; i++)
> +    {
> +      if (atomic_load_explicit (&done, memory_order_acquire) != 0)
> +	break;
> +      t2 = xpthread_create (0, nop, 0);
> +      xpthread_join (t2);
> +    }
> +
> +  xpthread_join (t1);
> +  printf ("threads created during dlopen: %d\n", i);
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>

Ok, 

> diff --git a/elf/tst-tls21mod.c b/elf/tst-tls21mod.c
> new file mode 100644
> index 0000000000..206ece4fb3
> --- /dev/null
> +++ b/elf/tst-tls21mod.c
> @@ -0,0 +1 @@
> +int __thread x;
> 

Ok.