| Message ID | cda846784ce55a77519a5ea86b6b073899a20ab6.1537285751.git.jstancek@redhat.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | mem/mmapstress10: fix hangs with recent glibc | expand |
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=<optimized out>) at mmapstress10.c:898 > #4 <signal handler called> > #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=<optimized out>, > nprocs=nprocs@entry=20) at mmapstress10.c:676 > #8 0x0000000000403833 in main (argc=<optimized out>, argv=<optimized 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.
----- 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=<optimized out>) at > > mmapstress10.c:898 > > #4 <signal handler called> > > #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=<optimized out>, > > nprocs=nprocs@entry=20) at mmapstress10.c:676 > > #8 0x0000000000403833 in main (argc=<optimized out>, argv=<optimized > > 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
diff --git a/testcases/kernel/mem/mmapstress/mmapstress10.c b/testcases/kernel/mem/mmapstress/mmapstress10.c index 482933bcec79..cf8403ef4b36 100644 --- a/testcases/kernel/mem/mmapstress/mmapstress10.c +++ b/testcases/kernel/mem/mmapstress/mmapstress10.c @@ -887,7 +887,7 @@ int fileokay(char *file, uchar_t * expbuf) { if (!leavefile) (void)unlink(filename); - exit(1); + _exit(1); } void clean_mapper(int sig) @@ -895,14 +895,14 @@ void clean_mapper(int sig) if (fd_mapper) close(fd_mapper); munmap(maddr_mapper, mapsize_mapper); - exit(0); + _exit(0); } void clean_writer(int sig) { if (fd_writer) close(fd_writer); - exit(0); + _exit(0); } unsigned int initrand(void)
There haven't been any major changes to this test in years, so presumably something in recent glibc changed, that exposed this problem. 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=<optimized out>) at mmapstress10.c:898 #4 <signal handler called> #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=<optimized out>, nprocs=nprocs@entry=20) at mmapstress10.c:676 #8 0x0000000000403833 in main (argc=<optimized out>, argv=<optimized out>) at mmapstress10.c:458 Switch all signal handlers to _exit(). Signed-off-by: Jan Stancek <jstancek@redhat.com> --- testcases/kernel/mem/mmapstress/mmapstress10.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)