On Fri, Oct 02, 2020 at 11:01:34PM +0530, Naresh Kamboju wrote: > On Thu, 24 Sep 2020 at 21:51, Christian Brauner > <christian.brauner@xxxxxxxxxx> wrote: > > > > On Thu, Sep 24, 2020 at 04:33:17PM +0200, Christian Brauner wrote: > > > On Wed, Sep 23, 2020 at 07:52:05PM +0530, Naresh Kamboju wrote: > > > > selftests: pidfd: pidfd_wait hangs on linux next kernel on x86_64, > > > > i386 and arm64 Juno-r2 > > > > These devices are using NFS mounted rootfs. > > > > I have tested pidfd testcases independently and all test PASS. > > > > > > > > The Hang or exit from test run noticed when run by run_kselftest.sh > > > > > > > > pidfd_wait.c:208:wait_nonblock:Expected sys_waitid(P_PIDFD, pidfd, > > > > &info, WSTOPPED, NULL) (-1) == 0 (0) > > > > wait_nonblock: Test terminated by assertion > > > > > > > > metadata: > > > > git branch: master > > > > git repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > > > git commit: e64997027d5f171148687e58b78c8b3c869a6158 > > > > git describe: next-20200922 > > > > make_kernelversion: 5.9.0-rc6 > > > > kernel-config: > > > > http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/intel-core2-32/lkft/linux-next/865/config > > > > > > > > Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> > > > > > > Thanks for reproting this. I'm taking a look now! > > > > Ok, this is a simple race in the selftests, that I overlooked and which > > is more likely to hit when there's a lot of processes running on the > > system. Basically the child process hasn't SIGSTOPed itself yet but the > > parent is already calling waitid() on a O_NONBLOCK pidfd. Since it > > doesn't find a WSTOPPED process it returns -EAGAIN correctly. > > > > The fix for this is to move the line where we're removing the O_NONBLOCK > > property from the fd before the waitid() WSTOPPED call so we hang until > > the child becomes stopped. > > > > So I believe the fix is: > > I have tested this patch and the pidfd_wait test did not hang this time. > > Tested-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> > > test log link > https://lkft.validation.linaro.org/scheduler/job/1813223 Thanks for testing, Naresh. I've applied the patch: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/commit/?h=pidfd_o_nonblock&id=01361b665a26ef0c087e53f14cf310d1cfe0cf98 Christian
