http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51298
Bug #: 51298
Summary: libgomp team_barrier locking failures
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libgomp
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: amo...@gmail.com
There seems to be a locking related failure in the linux barrier
implementation, because libgomp testcases hang on power7. This is both before
and after the fix for http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51249
Here's a dump of some info from one of the hung tests that might help pin down
the problem. Then again, it might not. power7 quite aggressively speculates
reads, so I suspect a missing read barrier somewhere.
(gdb) bt
#0 0x00000fff91ebf36c in sys_futex0 (val=0, op=<optimized out>,
addr=0x100210d4) at
/home/amodra/src/gcc-current/libgomp/config/linux/powerpc/futex.h:48
#1 futex_wait (val=0, addr=0x100210d4) at
/home/amodra/src/gcc-current/libgomp/config/linux/powerpc/futex.h:61
#2 do_wait (val=0, addr=<optimized out>) at
/home/amodra/src/gcc-current/libgomp/config/linux/wait.h:64
#3 gomp_team_barrier_wait_end (bar=0x100210d0, state=0) at
/home/amodra/src/gcc-current/libgomp/config/linux/bar.c:109
#4 0x00000fff91eb7540 in GOMP_barrier () at
/home/amodra/src/gcc-current/libgomp/barrier.c:40
#5 0x0000000010000f10 in .test_barrier.822._omp_fn.2 () at
/home/amodra/src/gcc-current/libgomp/testsuite/libgomp.fortran/omp_parse2.f90:59
#6 0x0000000010000b90 in test_barrier () at
/home/amodra/src/gcc-current/libgomp/testsuite/libgomp.fortran/omp_parse2.f90:56
#7 MAIN__ () at
/home/amodra/src/gcc-current/libgomp/testsuite/libgomp.fortran/omp_parse2.f90:5
#8 main (argc=<optimized out>, argv=<optimized out>) at
/home/amodra/src/gcc-current/libgomp/testsuite/libgomp.fortran/omp_parse2.f90:2
#9 0x00000fff91ccf05c in .generic_start_main () from /lib64/power7/libc.so.6
#10 0x00000fff91ccf27c in .__libc_start_main () from /lib64/power7/libc.so.6
#11 0x0000000000000000 in ?? ()
(gdb) up 3
#3 gomp_team_barrier_wait_end (bar=0x100210d0, state=0) at
/home/amodra/src/gcc-current/libgomp/config/linux/bar.c:109
(gdb) p *bar
$1 = {total = 4, generation = 0, awaited = 1}
(gdb) p state
$2 = 0
(gdb) p generation
$3 = 0
(gdb) p gomp_tls_data
$4 = {fn = 0, data = 0x0, ts = {team = 0x10021050, work_share = 0x10021150,
last_work_share = 0x0, team_id = 0, level = 1, active_level = 1, single_count =
0, static_trip = 0}, task = 0x10021568, release = {count = 0}, thread_pool =
0x10021760}
(gdb) p *gomp_tls_data.ts.team
$5 = {nthreads = 4, work_share_chunk = 8, prev_ts = {team = 0x0, work_share =
0x0, last_work_share = 0x0, team_id = 0, level = 0, active_level = 0,
single_count = 0, static_trip = 0}, master_release = {count = 0},
ordered_release = 0x10021708, work_share_list_alloc = 0x100211d0,
work_share_list_free = 0x0, single_count = 0, barrier = {total = 4, generation
= 0, awaited = 1}, work_shares = {{sched = GFS_RUNTIME, mode = 0, {{chunk_size
= 0, end = 0, incr = 0}, {chunk_size_ull = 0, end_ull = 0, incr_ull = 0}},
ordered_team_ids = 0x0, ordered_num_used = 0, ordered_owner = 0, ordered_cur =
0, next_alloc = 0x0, lock = {flag = 0}, threads_completed = 0, {next = 0,
next_ull = 0, copyprivate = 0x0}, {next_ws = 0x0, next_free = 0x0},
inline_ordered_team_ids = 0x100211a8}, {sched = GFS_RUNTIME, mode = 0,
{{chunk_size = 0, end = 0, incr = 0}, {chunk_size_ull = 0, end_ull = 0,
incr_ull = 0}}, ordered_team_ids = 0x0, ordered_num_used = 0, ordered_owner =
0, ordered_cur = 0, next_alloc = 0x0, lock = {flag = 0}, threads_completed = 0,
{next = 0, next_ull = 0, copyprivate = 0x0}, {next_ws = 0x10021250, next_free =
0x10021250}, inline_ordered_team_ids = 0x10021228}, {sched = GFS_RUNTIME, mode
= 0, {{chunk_size = 0, end = 0, incr = 0}, {chunk_size_ull = 0, end_ull = 0,
incr_ull = 0}}, ordered_team_ids = 0x0, ordered_num_used = 0, ordered_owner =
0, ordered_cur = 0, next_alloc = 0x0, lock = {flag = 0}, threads_completed = 0,
{next = 0, next_ull = 0, copyprivate = 0x0}, {next_ws = 0x100212d0, next_free =
0x100212d0}, inline_ordered_team_ids = 0x100212a8}, {sched = GFS_RUNTIME, mode
= 0, {{chunk_size = 0, end = 0, incr = 0}, {chunk_size_ull = 0, end_ull = 0,
incr_ull = 0}}, ordered_team_ids = 0x0, ordered_num_used = 0, ordered_owner =
0, ordered_cur = 0, next_alloc = 0x0, lock = {flag = 0}, threads_completed = 0,
{next = 0, next_ull = 0, copyprivate = 0x0}, {next_ws = 0x10021350, next_free =
0x10021350}, inline_ordered_team_ids = 0x10021328}, {sched = GFS_RUNTIME, mode
= 0, {{chunk_size = 0, end = 0, incr = 0}, {chunk_size_ull = 0, end_ull = 0,
incr_ull = 0}}, ordered_team_ids = 0x0, ordered_num_used = 0, ordered_owner =
0, ordered_cur = 0, next_alloc = 0x0, lock = {flag = 0}, threads_completed = 0,
{next = 0, next_ull = 0, copyprivate = 0x0}, {next_ws = 0x100213d0, next_free =
0x100213d0}, inline_ordered_team_ids = 0x100213a8}, {sched = GFS_RUNTIME, mode
= 0, {{chunk_size = 0, end = 0, incr = 0}, {chunk_size_ull = 0, end_ull = 0,
incr_ull = 0}}, ordered_team_ids = 0x0, ordered_num_used = 0, ordered_owner =
0, ordered_cur = 0, next_alloc = 0x0, lock = {flag = 0}, threads_completed = 0,
{next = 0, next_ull = 0, copyprivate = 0x0}, {next_ws = 0x10021450, next_free =
0x10021450}, inline_ordered_team_ids = 0x10021428}, {sched = GFS_RUNTIME, mode
= 0, {{chunk_size = 0, end = 0, incr = 0}, {chunk_size_ull = 0, end_ull = 0,
incr_ull = 0}}, ordered_team_ids = 0x0, ordered_num_used = 0, ordered_owner =
0, ordered_cur = 0, next_alloc = 0x0, lock = {flag = 0}, threads_completed = 0,
{next = 0, next_ull = 0, copyprivate = 0x0}, {next_ws = 0x100214d0, next_free =
0x100214d0}, inline_ordered_team_ids = 0x100214a8}, {sched = GFS_RUNTIME, mode
= 0, {{chunk_size = 0, end = 0, incr = 0}, {chunk_size_ull = 0, end_ull = 0,
incr_ull = 0}}, ordered_team_ids = 0x0, ordered_num_used = 0, ordered_owner =
0, ordered_cur = 0, next_alloc = 0x0, lock = {flag = 0}, threads_completed = 0,
{next = 0, next_ull = 0, copyprivate = 0x0}, {next_ws = 0x0, next_free = 0x0},
inline_ordered_team_ids = 0x10021528}}, task_lock = {flag = 0}, task_queue =
0x0, task_count = 0, task_running_count = 0, implicit_task = 0x10021568}
(gdb) p *gomp_tls_data.ts.work_share
$6 = {sched = GFS_RUNTIME, mode = 0, {{chunk_size = 0, end = 0, incr = 0},
{chunk_size_ull = 0, end_ull = 0, incr_ull = 0}}, ordered_team_ids = 0x0,
ordered_num_used = 0, ordered_owner = 0, ordered_cur = 0, next_alloc = 0x0,
lock = {flag = 0}, threads_completed = 0, {next = 0, next_ull = 0, copyprivate
= 0x0}, {next_ws = 0x0, next_free = 0x0}, inline_ordered_team_ids = 0x100211a8}
