Re: [dpdk-dev] [PATCH v2] test: fix debug autotest with eal cleanup addition

[Thomas Monjalon <thomas@monjalon.net>]

31/01/2018 14:53, Ananyev, Konstantin:
> Hi Harry,
> 
> From: Harry van Haaren
> > 
> > Before this patch, the debug_autotest would call fork(),
> > call rte_panic() or rte_exit() in the child process, and
> > examine the return code to verify that rte_panic() and
> > rte_exit() were correctly reporting failures.
> > 
> > With the inclusion of the rte_eal_cleanup() patch, rte_exit()
> > was modified to cleanly tear-down EAL allocations. Currently
> > only one library (service cores) is allocated by EAL at startup
> > and should be cleaned up. This library has a check on a normal
> > (non-hugepage) variable to protect against double cleanup. The
> > service cores finalize() function itself frees back hugepage mem.
> > 
> > Given the fork() approach from the unit test, and the fact that
> > the double-free check is on an ordinary variable, causes multiple
> > child processed (fork()-ed from the unit-test runner) to attempt
> > to free the huge-page memory multiple times. The variable to
> > protect against double-cleanup was not effective, as the fork()
> > would restore it to show initialized in the next child.
> > 
> > The solution is to call rte_service_finalize() *before* calling
> > fork(), which results in the service cores double-cleanup variable
> > to be zero before the fork(), and hence the child processes never
> > free the hugepage service-cores memory (correct behavior, as the
> > unit-test suite is still running, and owns the hugepages).
> 
> Ok, you fixed it in UT, but what to do other apps that use fork()?
> Let say our examples/multi_process/l2fwd_fork uses fork() to
> spawn child processes instead of threads.
> Might be some generic way is needed: let say at fork time setup some
> global to indicate that it is a child process and it shouldn't call rte_finalize() or so.
> Konstantin

At first, we should discuss whether it is a good idea to support fork,
given that we have the "secondary process solution".

Then, if an improvement is needed, it should go in 18.05.
I think the fix in UT is good enough for 18.02.