From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Date: Thu, 23 Aug 2018 21:27:02 -0700 Subject: [LTP] [PATCH] syscalls/shmctl05.c: Fix ENOSPC error In-Reply-To: <1533108893-13078-1-git-send-email-yangx.jy@cn.fujitsu.com> References: <1533108893-13078-1-git-send-email-yangx.jy@cn.fujitsu.com> Message-ID: <20180824042701.GA12266@sol.localdomain> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it Hi Xiao, On Wed, Aug 01, 2018 at 03:34:53PM +0800, Xiao Yang wrote: > Running shmctl05 got the following error on some distros(e.g. RHEL7.5): > ------------------------------------------------------ > tst_safe_sysv_ipc.c:111: BROK: shmctl05.c:51: shmget(61455, 4096, 3c0) failed: ENOSPC > shmctl05.c:104: WARN: pthread_join(..., (nil)) failed: EDEADLK > tst_safe_sysv_ipc.c:111: BROK: shmctl05.c:81: shmget(61455, 4096, 3c0) failed: ENOSPC > ------------------------------------------------------- > > From shmctl(2) manpage, shmctl(IPC_RMID) just marks a shm segment to > be destroyed, and the segment will only actually be destroyed after > the last process detaches it (i.e., when the shm_nattch member of the > associated structure shmid_ds is zero). So it is possible for the > number of created shm segments to exceed the system-wide maximum number > (e.g. shmmni is 4096) if only shmctl(IPC_RMID) has been called. > > From shmdt(2) manpage, a successful shmdt(2) call will decrement > the shm_nattch by one. So we should call shmdt(2) to decrement > the shm_nattch to zero before calling shmctl(IPC_RMID). > > Add shmdt(2) to ensure that all shm segments are actually destroyed. > > Signed-off-by: Xiao Yang > --- > testcases/kernel/syscalls/ipc/shmctl/shmctl05.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/testcases/kernel/syscalls/ipc/shmctl/shmctl05.c b/testcases/kernel/syscalls/ipc/shmctl/shmctl05.c > index a960cc9..0eb0776 100644 > --- a/testcases/kernel/syscalls/ipc/shmctl/shmctl05.c > +++ b/testcases/kernel/syscalls/ipc/shmctl/shmctl05.c > @@ -92,6 +92,8 @@ static void do_test(void) > "Unexpected remap_file_pages() error"); > } > tst_fzsync_wait_a(&fzsync_pair); > + /* ensure that a shm segment will actually be destroyed */ > + SAFE_SHMDT(addr); > } > > tst_res(TPASS, "didn't crash"); > -- I think you missed part of the explanation for why this test (apparently) fails on old kernels. On recent kernels, remap_file_pages() *is* unmapping the shm segment, so the test passes. Perhaps the behavior of remap_file_pages() changed in v4.0 when its implementation was replaced with an emulation. Calling shmdt() is probably the right fix for the test, but you shouldn't call the SAFE_* version since shmdt() will fail with an error on recent kernels, which with the SAFE_* version would fail the test. - Eric