Message ID | 56F8FD46.1060400@codesourcery.com |
---|---|
State | New |
Headers | show |
Ping. On 2016/3/28 05:45 PM, Chung-Lin Tang wrote: > Hi Jakub, there's a path for deadlock on acc_device_lock when going > through the acc_set_device_type() OpenACC library function. > Basically, the gomp_init_targets_once() function should not be > called with that held. The attached patch moves it appropriately. > > Also in this patch, there are several cases in acc_* functions > where gomp_init_targets_once() is guarded by a test of > !cached_base_dev. Since that function already uses pthread_once() to > call gomp_target_init(), and technically cached_base_dev > is protected by acc_device_lock, the cleanest way should be to > simply drop those "if(!cached_base_dev)" tests. > > Tested libgomp without regressions on an nvptx offloaded system, > is this okay for trunk? > > Thanks, > Chung-Lin > > 2016-03-28 Chung-Lin Tang <cltang@codesourcery.com> > > * oacc-init.c (acc_init): Remove !cached_base_dev condition on call to > gomp_init_targets_once(). > (acc_set_device_type): Remove !cached_base_dev condition on call to > gomp_init_targets_once(), move call to before acc_device_lock acquire, > to avoid deadlock. > (acc_get_device_num): Remove !cached_base_dev condition on call to > gomp_init_targets_once(). > (acc_set_device_num): Likewise. >
Ping x2. Hi Jakub, This patch is fairly straightforward, and solves a easily encountered deadlock. Please approve for trunk and gcc-6-branch. Thanks, Chung-Lin On 2016/4/16 03:39 PM, Chung-Lin Tang wrote: > Ping. > > On 2016/3/28 05:45 PM, Chung-Lin Tang wrote: >> Hi Jakub, there's a path for deadlock on acc_device_lock when going >> through the acc_set_device_type() OpenACC library function. >> Basically, the gomp_init_targets_once() function should not be >> called with that held. The attached patch moves it appropriately. >> >> Also in this patch, there are several cases in acc_* functions >> where gomp_init_targets_once() is guarded by a test of >> !cached_base_dev. Since that function already uses pthread_once() to >> call gomp_target_init(), and technically cached_base_dev >> is protected by acc_device_lock, the cleanest way should be to >> simply drop those "if(!cached_base_dev)" tests. >> >> Tested libgomp without regressions on an nvptx offloaded system, >> is this okay for trunk? >> >> Thanks, >> Chung-Lin >> >> 2016-03-28 Chung-Lin Tang <cltang@codesourcery.com> >> >> * oacc-init.c (acc_init): Remove !cached_base_dev condition on call to >> gomp_init_targets_once(). >> (acc_set_device_type): Remove !cached_base_dev condition on call to >> gomp_init_targets_once(), move call to before acc_device_lock acquire, >> to avoid deadlock. >> (acc_get_device_num): Remove !cached_base_dev condition on call to >> gomp_init_targets_once(). >> (acc_set_device_num): Likewise. >> >
Ping x3 On 2016/4/19 10:30 PM, Chung-Lin Tang wrote: > Ping x2. > > Hi Jakub, > This patch is fairly straightforward, and solves a easily encountered > deadlock. Please approve for trunk and gcc-6-branch. > > Thanks, > Chung-Lin > > On 2016/4/16 03:39 PM, Chung-Lin Tang wrote: >> Ping. >> >> On 2016/3/28 05:45 PM, Chung-Lin Tang wrote: >>> Hi Jakub, there's a path for deadlock on acc_device_lock when going >>> through the acc_set_device_type() OpenACC library function. >>> Basically, the gomp_init_targets_once() function should not be >>> called with that held. The attached patch moves it appropriately. >>> >>> Also in this patch, there are several cases in acc_* functions >>> where gomp_init_targets_once() is guarded by a test of >>> !cached_base_dev. Since that function already uses pthread_once() to >>> call gomp_target_init(), and technically cached_base_dev >>> is protected by acc_device_lock, the cleanest way should be to >>> simply drop those "if(!cached_base_dev)" tests. >>> >>> Tested libgomp without regressions on an nvptx offloaded system, >>> is this okay for trunk? >>> >>> Thanks, >>> Chung-Lin >>> >>> 2016-03-28 Chung-Lin Tang <cltang@codesourcery.com> >>> >>> * oacc-init.c (acc_init): Remove !cached_base_dev condition on call to >>> gomp_init_targets_once(). >>> (acc_set_device_type): Remove !cached_base_dev condition on call to >>> gomp_init_targets_once(), move call to before acc_device_lock acquire, >>> to avoid deadlock. >>> (acc_get_device_num): Remove !cached_base_dev condition on call to >>> gomp_init_targets_once(). >>> (acc_set_device_num): Likewise. >>> >> >
On Mon, Mar 28, 2016 at 05:45:42PM +0800, Chung-Lin Tang wrote: > Hi Jakub, there's a path for deadlock on acc_device_lock when going > through the acc_set_device_type() OpenACC library function. > Basically, the gomp_init_targets_once() function should not be > called with that held. The attached patch moves it appropriately. > > Also in this patch, there are several cases in acc_* functions > where gomp_init_targets_once() is guarded by a test of > !cached_base_dev. Since that function already uses pthread_once() to > call gomp_target_init(), and technically cached_base_dev > is protected by acc_device_lock, the cleanest way should be to > simply drop those "if(!cached_base_dev)" tests. > > Tested libgomp without regressions on an nvptx offloaded system, > is this okay for trunk? Ok, with ChangeLog nits: > > 2016-03-28 Chung-Lin Tang <cltang@codesourcery.com> > > * oacc-init.c (acc_init): Remove !cached_base_dev condition on call to > gomp_init_targets_once(). > (acc_set_device_type): Remove !cached_base_dev condition on call to > gomp_init_targets_once(), move call to before acc_device_lock acquire, > to avoid deadlock. > (acc_get_device_num): Remove !cached_base_dev condition on call to > gomp_init_targets_once(). > (acc_set_device_num): Likewise. Please just use gomp_init_targets_once instead of gomp_init_targets_once() in the ChangeLog. > Index: oacc-init.c > =================================================================== > --- oacc-init.c (revision 234502) > +++ oacc-init.c (working copy) > @@ -433,8 +433,7 @@ goacc_attach_host_thread_to_device (int ord) > void > acc_init (acc_device_t d) > { > - if (!cached_base_dev) > - gomp_init_targets_once (); > + gomp_init_targets_once (); > > gomp_mutex_lock (&acc_device_lock); > > @@ -498,11 +497,10 @@ acc_set_device_type (acc_device_t d) > struct gomp_device_descr *base_dev, *acc_dev; > struct goacc_thread *thr = goacc_thread (); > > + gomp_init_targets_once (); > + > gomp_mutex_lock (&acc_device_lock); > > - if (!cached_base_dev) > - gomp_init_targets_once (); > - > cached_base_dev = base_dev = resolve_device (d, true); > acc_dev = &base_dev[goacc_device_num]; > > @@ -563,8 +561,7 @@ acc_get_device_num (acc_device_t d) > if (d >= _ACC_device_hwm) > gomp_fatal ("unknown device type %u", (unsigned) d); > > - if (!cached_base_dev) > - gomp_init_targets_once (); > + gomp_init_targets_once (); > > gomp_mutex_lock (&acc_device_lock); > dev = resolve_device (d, true); > @@ -584,8 +581,7 @@ acc_set_device_num (int ord, acc_device_t d) > struct gomp_device_descr *base_dev, *acc_dev; > int num_devices; > > - if (!cached_base_dev) > - gomp_init_targets_once (); > + gomp_init_targets_once (); > > if (ord < 0) > ord = goacc_device_num; Jakub
Index: oacc-init.c =================================================================== --- oacc-init.c (revision 234502) +++ oacc-init.c (working copy) @@ -433,8 +433,7 @@ goacc_attach_host_thread_to_device (int ord) void acc_init (acc_device_t d) { - if (!cached_base_dev) - gomp_init_targets_once (); + gomp_init_targets_once (); gomp_mutex_lock (&acc_device_lock); @@ -498,11 +497,10 @@ acc_set_device_type (acc_device_t d) struct gomp_device_descr *base_dev, *acc_dev; struct goacc_thread *thr = goacc_thread (); + gomp_init_targets_once (); + gomp_mutex_lock (&acc_device_lock); - if (!cached_base_dev) - gomp_init_targets_once (); - cached_base_dev = base_dev = resolve_device (d, true); acc_dev = &base_dev[goacc_device_num]; @@ -563,8 +561,7 @@ acc_get_device_num (acc_device_t d) if (d >= _ACC_device_hwm) gomp_fatal ("unknown device type %u", (unsigned) d); - if (!cached_base_dev) - gomp_init_targets_once (); + gomp_init_targets_once (); gomp_mutex_lock (&acc_device_lock); dev = resolve_device (d, true); @@ -584,8 +581,7 @@ acc_set_device_num (int ord, acc_device_t d) struct gomp_device_descr *base_dev, *acc_dev; int num_devices; - if (!cached_base_dev) - gomp_init_targets_once (); + gomp_init_targets_once (); if (ord < 0) ord = goacc_device_num;