From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cyril Hrubis Date: Wed, 19 Sep 2018 09:25:18 +0200 Subject: [LTP] [PATCH] mem/mmapstress10: fix hangs with recent glibc In-Reply-To: References: Message-ID: <20180919072518.GA28540@rei> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ltp@lists.linux.it 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=) 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. -- Cyril Hrubis chrubis@suse.cz