Re: [PATCH] Tweak test-*exit-race tests to honor the maximum number of processes

[Carlos O'Donell <carlos at redhat dot com>]

On 01/30/2018 08:54 AM, Dmitry V. Levin wrote:
> When the number of threads created by test-*exit-race tests is close
> to the maximum number of simultaneous processes per uid, these tests
> fail with the following diagnostics:
> 
> error: xpthread_check_return.c:32: pthread_create: Resource temporarily unavailable
> 
> Workaround this issue by limiting the number of threads created
> by these tests to sysconf (_SC_CHILD_MAX) / 2.
> 
> Tested that these tests still fail reliably on x86_64 with glibc-2.26
> and sysconf (_SC_CHILD_MAX) == 512.
> 
> *  stdlib/test-atexit-race-common.c: Include <unistd.h>.
> (kNumThreads): Remove const qualifier.
> (do_test): Limit kNumThreads to sysconf (_SC_CHILD_MAX) / 2.

The test should return UNSUPPORTED if an expected minimum number of threads
required to reliably trigger the test cannot be created e.g. 512.

> ---
>  ChangeLog                        |  6 ++++++
>  stdlib/test-atexit-race-common.c | 10 ++++++++--
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/stdlib/test-atexit-race-common.c b/stdlib/test-atexit-race-common.c
> index 4d7f911..7a65264 100644
> --- a/stdlib/test-atexit-race-common.c
> +++ b/stdlib/test-atexit-race-common.c
> @@ -33,10 +33,11 @@
>  
>  #include <stdio.h>
>  #include <stdlib.h>
> +#include <unistd.h>
>  #include <support/xthread.h>
>  
> -const size_t kNumThreads = 1024;
> -const size_t kNumHandlers = 1024;
> +static size_t kNumThreads = 1024;
> +static const size_t kNumHandlers = 1024;
>  
>  static void *
>  threadfunc (void *unused)
> @@ -62,6 +63,11 @@ do_test (void)
>       128KiB for a maximum required VM size of 128MiB.  */
>    xpthread_attr_setstacksize (&attr, 128 * 1024);
>  
> +  long nproc = sysconf (_SC_CHILD_MAX);
> +
> +  if (nproc > 0 && nproc / 2 < kNumThreads)
> +    kNumThreads = nproc / 2;
> +
>    for (i = 0; i < kNumThreads; ++i) {
>      xpthread_create (&attr, threadfunc, NULL);
>    }
> 


-- 
Cheers,
Carlos.