From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Stancek Date: Wed, 19 Sep 2018 03:32:52 -0400 (EDT) Subject: [LTP] [PATCH] mem/mmapstress10: fix hangs with recent glibc In-Reply-To: <20180919072518.GA28540@rei> References: <20180919072518.GA28540@rei> Message-ID: <264028361.49497270.1537342372589.JavaMail.zimbra@redhat.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it ----- Original Message ----- > Hi! > > There haven't been any major changes to this test in years, > > so presumably something in recent glibc changed, that exposed > > this problem. > > I guess that it may have been elsewhere as well, such as kernel > scheduller changes, etc. > > > I confirmed with glibc-2.28, that this test can hang quite reliably > > on 2 CPU KVM guest. It reproduces easier with smaller number of loops > > for child_mapper() and overall test runtime reduced (-p 20 -t 0.02). > > > > The problem is that childs' signal handler and main function both > > call exit(), which can deadlock on __exit_funcs_lock: > > > > #0 0x00007f0619d72f8c in __lll_lock_wait_private () from > > /lib64/libc.so.6 > > #1 0x00007f0619ca2f4b in __run_exit_handlers () from /lib64/libc.so.6 > > #2 0x00007f0619ca3160 in exit () from /lib64/libc.so.6 > > #3 0x00000000004039d8 in clean_mapper (sig=) at > > mmapstress10.c:898 > > #4 > > #5 0x00007f0619ca2fbd in __run_exit_handlers () from /lib64/libc.so.6 > > #6 0x00007f0619ca3160 in exit () from /lib64/libc.so.6 > > #7 0x0000000000403e7f in child_mapper (file=file@entry=0x40f530 > > "mmapstress10.out", procno=, > > nprocs=nprocs@entry=20) at mmapstress10.c:676 > > #8 0x0000000000403833 in main (argc=, argv= > out>) at mmapstress10.c:458 > > > > Switch all signal handlers to _exit(). > > Looks like a reasonable band aid for the problem. I looked shortly at > the source code and anything cleaner would require larger rewrite, so > acked. Pushed. Regards, Jan