From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Gruenbacher Subject: Re: [RFC][PATCH] wake_up_var() memory ordering Date: Tue, 25 Jun 2019 11:19:35 +0200 Message-ID: References: <20190624165012.GH3436@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20190624165012.GH3436@hirez.programming.kicks-ass.net> Sender: owner-linux-aio@kvack.org To: Peter Zijlstra Cc: David Howells , Paul McKenney , Will Deacon , Marcel Holtmann , Johan Hedberg , Matthias Brugger , Sean Wang , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , Alasdair Kergon , Mike Snitzer , dm-devel@redhat.com, Antti Palosaari , MauroCarvalho Chehab , Alexander Viro , Benjamin LaHaise , Chris Mason , Josef Bacik , David Sterba , Steve French , Bob Peterson List-Id: linux-rdma@vger.kernel.org Peter, thanks for the fixes. On Mon, 24 Jun 2019 at 18:53, Peter Zijlstra wrote: > Hi all, > > I tried using wake_up_var() today and accidentally noticed that it > didn't imply an smp_mb() and specifically requires it through > wake_up_bit() / waitqueue_active(). > > Now, wake_up_bit() doesn't imply the barrier because it is assumed to be > used with the atomic bitops API which either implies (test_and_clear) or > only needs smp_mb__after_atomic(), which is 'much' cheaper than an > unconditional smp_mb(). > > Still, while auditing all that, I found a whole bunch of things that > could be improved. There were missing barriers, superfluous barriers and > a whole bunch of sites that could use clear_and_wake_up_bit(). > > So this fixes all wake_up_bit() usage without actually changing > semantics of it (which are unfortunate but understandable). thanks for the fixes. > This does > however change the semantics of wake_up_var(); even though wake_up_var() > is most often used with atomics and then the additional smp_mb() is most > often superfluous :/ > > There isn't really a good option here, comments (other than I need to > split this up)? > > > --- > drivers/bluetooth/btmtksdio.c | 5 +---- > drivers/bluetooth/btmtkuart.c | 5 +---- > drivers/bluetooth/hci_mrvl.c | 8 ++------ > drivers/gpu/drm/i915/i915_reset.c | 6 ++---- > drivers/md/dm-bufio.c | 10 ++-------- > drivers/media/usb/dvb-usb-v2/dvb_usb_core.c | 15 ++++----------- > fs/afs/fs_probe.c | 1 + > fs/afs/server.c | 1 + > fs/afs/vl_probe.c | 1 + > fs/afs/volume.c | 1 + > fs/aio.c | 4 +--- > fs/block_dev.c | 1 + > fs/btrfs/extent_io.c | 4 +--- > fs/cachefiles/namei.c | 1 + > fs/cifs/connect.c | 3 +-- > fs/cifs/misc.c | 15 +++++---------- > fs/fscache/cookie.c | 2 ++ > fs/fscache/object.c | 2 ++ > fs/fscache/page.c | 3 +++ > fs/gfs2/glock.c | 8 ++------ > fs/gfs2/glops.c | 1 + > fs/gfs2/lock_dlm.c | 8 ++------ > fs/gfs2/recovery.c | 4 +--- > fs/gfs2/super.c | 1 + > fs/gfs2/sys.c | 4 +--- > fs/nfs/nfs4state.c | 4 +--- > fs/nfs/pnfs_nfs.c | 4 +--- > fs/nfsd/nfs4recover.c | 4 +--- > fs/orangefs/file.c | 2 +- > kernel/sched/wait_bit.c | 1 + > net/bluetooth/hci_event.c | 5 +---- > net/rds/ib_recv.c | 1 + > security/keys/gc.c | 5 ++--- > 33 files changed, 50 insertions(+), 90 deletions(-) > > diff --git a/drivers/bluetooth/btmtksdio.c b/drivers/bluetooth/btmtksdio.c > index 813338288453..27523cfeac9a 100644 > --- a/drivers/bluetooth/btmtksdio.c > +++ b/drivers/bluetooth/btmtksdio.c > @@ -356,11 +356,8 @@ static int btmtksdio_recv_event(struct hci_dev *hdev, struct sk_buff *skb) > > if (hdr->evt == HCI_EV_VENDOR) { > if (test_and_clear_bit(BTMTKSDIO_TX_WAIT_VND_EVT, > - &bdev->tx_state)) { > - /* Barrier to sync with other CPUs */ > - smp_mb__after_atomic(); > + &bdev->tx_state)) > wake_up_bit(&bdev->tx_state, BTMTKSDIO_TX_WAIT_VND_EVT); > - } > } > > return 0; > diff --git a/drivers/bluetooth/btmtkuart.c b/drivers/bluetooth/btmtkuart.c > index f5dbeec8e274..7fe324df3799 100644 > --- a/drivers/bluetooth/btmtkuart.c > +++ b/drivers/bluetooth/btmtkuart.c > @@ -340,11 +340,8 @@ static int btmtkuart_recv_event(struct hci_dev *hdev, struct sk_buff *skb) > > if (hdr->evt == HCI_EV_VENDOR) { > if (test_and_clear_bit(BTMTKUART_TX_WAIT_VND_EVT, > - &bdev->tx_state)) { > - /* Barrier to sync with other CPUs */ > - smp_mb__after_atomic(); > + &bdev->tx_state)) > wake_up_bit(&bdev->tx_state, BTMTKUART_TX_WAIT_VND_EVT); > - } > } > > return 0; > diff --git a/drivers/bluetooth/hci_mrvl.c b/drivers/bluetooth/hci_mrvl.c > index 50212ac629e3..f03294d39d08 100644 > --- a/drivers/bluetooth/hci_mrvl.c > +++ b/drivers/bluetooth/hci_mrvl.c > @@ -157,9 +157,7 @@ static int mrvl_recv_fw_req(struct hci_dev *hdev, struct sk_buff *skb) > > mrvl->tx_len = le16_to_cpu(pkt->lhs); > > - clear_bit(STATE_FW_REQ_PENDING, &mrvl->flags); > - smp_mb__after_atomic(); > - wake_up_bit(&mrvl->flags, STATE_FW_REQ_PENDING); > + clear_and_wake_up_bit(STATE_FW_REQ_PENDING, &mrvl->flags); > > done: > kfree_skb(skb); > @@ -192,9 +190,7 @@ static int mrvl_recv_chip_ver(struct hci_dev *hdev, struct sk_buff *skb) > > bt_dev_info(hdev, "Controller id = %x, rev = %x", mrvl->id, mrvl->rev); > > - clear_bit(STATE_CHIP_VER_PENDING, &mrvl->flags); > - smp_mb__after_atomic(); > - wake_up_bit(&mrvl->flags, STATE_CHIP_VER_PENDING); > + clear_and_wake_up_bit(STATE_CHIP_VER_PENDING, &mrvl->flags); > > done: > kfree_skb(skb); > diff --git a/drivers/gpu/drm/i915/i915_reset.c b/drivers/gpu/drm/i915/i915_reset.c > index 677d59304e78..6809367dbfa9 100644 > --- a/drivers/gpu/drm/i915/i915_reset.c > +++ b/drivers/gpu/drm/i915/i915_reset.c > @@ -1324,10 +1324,8 @@ void i915_handle_error(struct drm_i915_private *i915, > if (i915_reset_engine(engine, msg) == 0) > engine_mask &= ~engine->mask; > > - clear_bit(I915_RESET_ENGINE + engine->id, > - &error->flags); > - wake_up_bit(&error->flags, > - I915_RESET_ENGINE + engine->id); > + clear_and_wake_up_bit(I915_RESET_ENGINE + engine->id, > + &error->flags); > } > } > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > index 2a48ea3f1b30..3114836cc717 100644 > --- a/drivers/md/dm-bufio.c > +++ b/drivers/md/dm-bufio.c > @@ -667,10 +667,7 @@ static void write_endio(struct dm_buffer *b, blk_status_t status) > BUG_ON(!test_bit(B_WRITING, &b->state)); > > smp_mb__before_atomic(); > - clear_bit(B_WRITING, &b->state); > - smp_mb__after_atomic(); > - > - wake_up_bit(&b->state, B_WRITING); > + clear_and_wake_up_bit(B_WRITING, &b->state); > } > > /* > @@ -1045,10 +1042,7 @@ static void read_endio(struct dm_buffer *b, blk_status_t status) > BUG_ON(!test_bit(B_READING, &b->state)); > > smp_mb__before_atomic(); > - clear_bit(B_READING, &b->state); > - smp_mb__after_atomic(); > - > - wake_up_bit(&b->state, B_READING); > + clear_and_wake_up_bit(B_READING, &b->state); > } > > /* > diff --git a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c > index e5e056bf9dfa..fa46bc930704 100644 > --- a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c > +++ b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c > @@ -374,9 +374,7 @@ static int dvb_usb_stop_feed(struct dvb_demux_feed *dvbdmxfeed) > usb_urb_killv2(&adap->stream); > > /* clear 'streaming' status bit */ > - clear_bit(ADAP_STREAMING, &adap->state_bits); > - smp_mb__after_atomic(); > - wake_up_bit(&adap->state_bits, ADAP_STREAMING); > + clear_and_wake_up_bit(ADAP_STREAMING, &adap->state_bits); > skip_feed_stop: > > if (ret) > @@ -578,11 +576,8 @@ static int dvb_usb_fe_init(struct dvb_frontend *fe) > goto err; > } > err: > - if (!adap->suspend_resume_active) { > - clear_bit(ADAP_INIT, &adap->state_bits); > - smp_mb__after_atomic(); > - wake_up_bit(&adap->state_bits, ADAP_INIT); > - } > + if (!adap->suspend_resume_active) > + clear_and_wake_up_bit(ADAP_INIT, &adap->state_bits); > > dev_dbg(&d->udev->dev, "%s: ret=%d\n", __func__, ret); > return ret; > @@ -619,9 +614,7 @@ static int dvb_usb_fe_sleep(struct dvb_frontend *fe) > err: > if (!adap->suspend_resume_active) { > adap->active_fe = -1; > - clear_bit(ADAP_SLEEP, &adap->state_bits); > - smp_mb__after_atomic(); > - wake_up_bit(&adap->state_bits, ADAP_SLEEP); > + clear_and_wake_up_bit(ADAP_SLEEP, &adap->state_bits); > } > > dev_dbg(&d->udev->dev, "%s: ret=%d\n", __func__, ret); > diff --git a/fs/afs/fs_probe.c b/fs/afs/fs_probe.c > index cfe62b154f68..377ee07d5f76 100644 > --- a/fs/afs/fs_probe.c > +++ b/fs/afs/fs_probe.c > @@ -18,6 +18,7 @@ static bool afs_fs_probe_done(struct afs_server *server) > > wake_up_var(&server->probe_outstanding); > clear_bit_unlock(AFS_SERVER_FL_PROBING, &server->flags); > + smp_mb__after_atomic(); > wake_up_bit(&server->flags, AFS_SERVER_FL_PROBING); > return true; > } > diff --git a/fs/afs/server.c b/fs/afs/server.c > index e900cd74361b..c9b74a397cc1 100644 > --- a/fs/afs/server.c > +++ b/fs/afs/server.c > @@ -569,6 +569,7 @@ bool afs_check_server_record(struct afs_fs_cursor *fc, struct afs_server *server > if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) { > success = afs_update_server_record(fc, server); > clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags); > + smp_mb__after_atomic(); > wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING); > _leave(" = %d", success); > return success; > diff --git a/fs/afs/vl_probe.c b/fs/afs/vl_probe.c > index 858498cc1b05..1939624aa147 100644 > --- a/fs/afs/vl_probe.c > +++ b/fs/afs/vl_probe.c > @@ -18,6 +18,7 @@ static bool afs_vl_probe_done(struct afs_vlserver *server) > > wake_up_var(&server->probe_outstanding); > clear_bit_unlock(AFS_VLSERVER_FL_PROBING, &server->flags); > + smp_mb__after_atomic(); > wake_up_bit(&server->flags, AFS_VLSERVER_FL_PROBING); > return true; > } > diff --git a/fs/afs/volume.c b/fs/afs/volume.c > index 08fdb3951c49..b968e4e96f6b 100644 > --- a/fs/afs/volume.c > +++ b/fs/afs/volume.c > @@ -303,6 +303,7 @@ int afs_check_volume_status(struct afs_volume *volume, struct key *key) > ret = afs_update_volume_status(volume, key); > clear_bit_unlock(AFS_VOLUME_WAIT, &volume->flags); > clear_bit_unlock(AFS_VOLUME_UPDATING, &volume->flags); > + smp_mb__after_atomic(); > wake_up_bit(&volume->flags, AFS_VOLUME_WAIT); > _leave(" = %d", ret); > return ret; > diff --git a/fs/aio.c b/fs/aio.c > index 3490d1fa0e16..a21acb7ee2a5 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -1154,9 +1154,7 @@ static void aio_complete(struct aio_kiocb *iocb) > * like in wake_up_bit() where clearing a bit has to be > * ordered with the unlocked test. > */ > - smp_mb(); > - > - if (waitqueue_active(&ctx->wait)) > + if (wq_has_sleeper(&ctx->wait)) > wake_up(&ctx->wait); > } > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 749f5984425d..80e35cbfc7cc 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -1687,6 +1687,7 @@ int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder) > /* tell others that we're done */ > BUG_ON(whole->bd_claiming != holder); > whole->bd_claiming = NULL; > + smp_mb(); > wake_up_bit(&whole->bd_claiming, 0); > > spin_unlock(&bdev_lock); > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index db337e53aab3..ee1136ae46fd 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -3683,9 +3683,7 @@ static noinline_for_stack int lock_extent_buffer_for_io(struct extent_buffer *eb > > static void end_extent_buffer_writeback(struct extent_buffer *eb) > { > - clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags); > - smp_mb__after_atomic(); > - wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK); > + clear_and_wake_up_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags); > } > > static void set_btree_ioerr(struct page *page) > diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c > index ecc8ecbbfa5a..ecebba72ec7d 100644 > --- a/fs/cachefiles/namei.c > +++ b/fs/cachefiles/namei.c > @@ -267,6 +267,7 @@ void cachefiles_mark_object_inactive(struct cachefiles_cache *cache, > clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags); > write_unlock(&cache->active_lock); > > + smp_mb__after_atomic(); > wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE); > > /* This object can now be culled, so we need to let the daemon know > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c > index 8c4121da624e..8c1115ed1c28 100644 > --- a/fs/cifs/connect.c > +++ b/fs/cifs/connect.c > @@ -5235,8 +5235,7 @@ cifs_sb_tlink(struct cifs_sb_info *cifs_sb) > } > > tlink->tl_tcon = cifs_construct_tcon(cifs_sb, fsuid); > - clear_bit(TCON_LINK_PENDING, &tlink->tl_flags); > - wake_up_bit(&tlink->tl_flags, TCON_LINK_PENDING); > + clear_and_wake_up_bit(TCON_LINK_PENDING, &tlink->tl_flags); > > if (IS_ERR(tlink->tl_tcon)) { > cifs_put_tlink(tlink); > diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c > index b1a696a73f7c..961751d89113 100644 > --- a/fs/cifs/misc.c > +++ b/fs/cifs/misc.c > @@ -584,10 +584,8 @@ int cifs_get_writer(struct cifsInodeInfo *cinode) > /* Check to see if we have started servicing an oplock break */ > if (test_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags)) { > cinode->writers--; > - if (cinode->writers == 0) { > - clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > - wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); > - } > + if (cinode->writers == 0) > + clear_and_wake_up_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > spin_unlock(&cinode->writers_lock); > goto start; > } > @@ -599,10 +597,8 @@ void cifs_put_writer(struct cifsInodeInfo *cinode) > { > spin_lock(&cinode->writers_lock); > cinode->writers--; > - if (cinode->writers == 0) { > - clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > - wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); > - } > + if (cinode->writers == 0) > + clear_and_wake_up_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > spin_unlock(&cinode->writers_lock); > } > > @@ -630,8 +626,7 @@ void cifs_queue_oplock_break(struct cifsFileInfo *cfile) > > void cifs_done_oplock_break(struct cifsInodeInfo *cinode) > { > - clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags); > - wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK); > + clear_and_wake_up_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags); > } > > bool > diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c > index 0ce39658a620..40ba8957ebf0 100644 > --- a/fs/fscache/cookie.c > +++ b/fs/fscache/cookie.c > @@ -381,6 +381,7 @@ void __fscache_enable_cookie(struct fscache_cookie *cookie, > > out_unlock: > clear_bit_unlock(FSCACHE_COOKIE_ENABLEMENT_LOCK, &cookie->flags); > + smp_mb__after_atomic(); > wake_up_bit(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK); > } > EXPORT_SYMBOL(__fscache_enable_cookie); > @@ -778,6 +779,7 @@ void __fscache_disable_cookie(struct fscache_cookie *cookie, > > out_unlock_enable: > clear_bit_unlock(FSCACHE_COOKIE_ENABLEMENT_LOCK, &cookie->flags); > + smp_mb__after_atomic(); > wake_up_bit(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK); > _leave(""); > } > diff --git a/fs/fscache/object.c b/fs/fscache/object.c > index cfeba839a0f2..08b2edec6596 100644 > --- a/fs/fscache/object.c > +++ b/fs/fscache/object.c > @@ -524,6 +524,7 @@ void fscache_object_lookup_negative(struct fscache_object *object) > > _debug("wake up lookup %p", &cookie->flags); > clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags); > + smp_mb__after_atomic(); > wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP); > } > _leave(""); > @@ -559,6 +560,7 @@ void fscache_obtained_object(struct fscache_object *object) > * to begin shovelling data. > */ > clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags); > + smp_mb__after_atomic(); > wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP); > } else { > fscache_stat(&fscache_n_object_created); > diff --git a/fs/fscache/page.c b/fs/fscache/page.c > index 26af6fdf1538..49ef238502a3 100644 > --- a/fs/fscache/page.c > +++ b/fs/fscache/page.c > @@ -113,6 +113,7 @@ bool __fscache_maybe_release_page(struct fscache_cookie *cookie, > fscache_stat(&fscache_n_store_vmscan_gone); > } > > + smp_mb(); > wake_up_bit(&cookie->flags, 0); > trace_fscache_wake_cookie(cookie); > if (xpage) > @@ -171,6 +172,7 @@ static void fscache_end_page_write(struct fscache_object *object, > trace_fscache_page(cookie, page, fscache_page_write_end_pend); > } > spin_unlock(&cookie->stores_lock); > + smp_mb(); > wake_up_bit(&cookie->flags, 0); > trace_fscache_wake_cookie(cookie); > } else { > @@ -922,6 +924,7 @@ void fscache_invalidate_writes(struct fscache_cookie *cookie) > put_page(results[i]); > } > > + smp_mb(); > wake_up_bit(&cookie->flags, 0); > trace_fscache_wake_cookie(cookie); > > diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c > index f1ebcb42cbf5..8024b6bdb6d4 100644 > --- a/fs/gfs2/glock.c > +++ b/fs/gfs2/glock.c > @@ -302,9 +302,7 @@ static inline int may_grant(const struct gfs2_glock *gl, const struct gfs2_holde > > static void gfs2_holder_wake(struct gfs2_holder *gh) > { > - clear_bit(HIF_WAIT, &gh->gh_iflags); > - smp_mb__after_atomic(); > - wake_up_bit(&gh->gh_iflags, HIF_WAIT); > + clear_and_wake_up_bit(HIF_WAIT, &gh->gh_iflags); > } > > /** > @@ -436,9 +434,7 @@ static void state_change(struct gfs2_glock *gl, unsigned int new_state) > static void gfs2_demote_wake(struct gfs2_glock *gl) > { > gl->gl_demote_state = LM_ST_EXCLUSIVE; > - clear_bit(GLF_DEMOTE, &gl->gl_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&gl->gl_flags, GLF_DEMOTE); > + clear_and_wake_up_bit(GLF_DEMOTE, &gl->gl_flags); > } > > /** > diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c > index cf4c767005b1..666629ea5da7 100644 > --- a/fs/gfs2/glops.c > +++ b/fs/gfs2/glops.c > @@ -227,6 +227,7 @@ static void gfs2_clear_glop_pending(struct gfs2_inode *ip) > return; > > clear_bit_unlock(GIF_GLOP_PENDING, &ip->i_flags); > + smp_mb__after_atomic(); > wake_up_bit(&ip->i_flags, GIF_GLOP_PENDING); This should become clear_and_wake_up_bit as well, right? There are several more instances of the same pattern. > } > > diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c > index 4361804646d8..0fa1865dd600 100644 > --- a/fs/gfs2/lock_dlm.c > +++ b/fs/gfs2/lock_dlm.c > @@ -1139,9 +1139,7 @@ static void gdlm_recover_done(void *arg, struct dlm_slot *slots, int num_slots, > if (!test_bit(DFL_UNMOUNT, &ls->ls_recover_flags)) > queue_delayed_work(gfs2_control_wq, &sdp->sd_control_work, 0); > > - clear_bit(DFL_DLM_RECOVERY, &ls->ls_recover_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&ls->ls_recover_flags, DFL_DLM_RECOVERY); > + clear_and_wake_up_bit(DFL_DLM_RECOVERY, &ls->ls_recover_flags); > spin_unlock(&ls->ls_recover_spin); > } > > @@ -1276,9 +1274,7 @@ static int gdlm_mount(struct gfs2_sbd *sdp, const char *table) > } > > ls->ls_first = !!test_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags); > - clear_bit(SDF_NOJOURNALID, &sdp->sd_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&sdp->sd_flags, SDF_NOJOURNALID); > + clear_and_wake_up_bit(SDF_NOJOURNALID, &sdp->sd_flags); > return 0; > > fail_release: > diff --git a/fs/gfs2/recovery.c b/fs/gfs2/recovery.c > index 2299a3fa1911..ef9a8ef6689b 100644 > --- a/fs/gfs2/recovery.c > +++ b/fs/gfs2/recovery.c > @@ -436,9 +436,7 @@ void gfs2_recover_func(struct work_struct *work) > jd->jd_recover_error = error; > gfs2_recovery_done(sdp, jd->jd_jid, LM_RD_GAVEUP); > done: > - clear_bit(JDF_RECOVERY, &jd->jd_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&jd->jd_flags, JDF_RECOVERY); > + clear_and_wake_up_bit(JDF_RECOVERY, &jd->jd_flags); > } > > int gfs2_recover_journal(struct gfs2_jdesc *jd, bool wait) > diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c > index b70cea5c8c59..28ff2e10bdd9 100644 > --- a/fs/gfs2/super.c > +++ b/fs/gfs2/super.c > @@ -985,6 +985,7 @@ void gfs2_freeze_func(struct work_struct *work) > } > deactivate_super(sb); > clear_bit_unlock(SDF_FS_FROZEN, &sdp->sd_flags); > + smp_mb__after_atomic(); > wake_up_bit(&sdp->sd_flags, SDF_FS_FROZEN); > return; > } > diff --git a/fs/gfs2/sys.c b/fs/gfs2/sys.c > index 159aedf63c2a..b337798d8957 100644 > --- a/fs/gfs2/sys.c > +++ b/fs/gfs2/sys.c > @@ -505,9 +505,7 @@ static ssize_t jid_store(struct gfs2_sbd *sdp, const char *buf, size_t len) > if (sdp->sd_args.ar_spectator && jid > 0) > rv = jid = -EINVAL; > sdp->sd_lockstruct.ls_jid = jid; > - clear_bit(SDF_NOJOURNALID, &sdp->sd_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&sdp->sd_flags, SDF_NOJOURNALID); > + clear_and_wake_up_bit(SDF_NOJOURNALID, &sdp->sd_flags); > out: > spin_unlock(&sdp->sd_jindex_spin); > return rv ? rv : len; > diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c > index e2e3c4f04d3e..a3ed413a38c5 100644 > --- a/fs/nfs/nfs4state.c > +++ b/fs/nfs/nfs4state.c > @@ -1196,9 +1196,7 @@ static int nfs4_run_state_manager(void *); > static void nfs4_clear_state_manager_bit(struct nfs_client *clp) > { > smp_mb__before_atomic(); > - clear_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state); > - smp_mb__after_atomic(); > - wake_up_bit(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING); > + clear_and_wake_up_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state); > rpc_wake_up(&clp->cl_rpcwaitq); > } > > diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c > index c0046c348910..37c4fe5a595c 100644 > --- a/fs/nfs/pnfs_nfs.c > +++ b/fs/nfs/pnfs_nfs.c > @@ -567,9 +567,7 @@ static void nfs4_wait_ds_connect(struct nfs4_pnfs_ds *ds) > static void nfs4_clear_ds_conn_bit(struct nfs4_pnfs_ds *ds) > { > smp_mb__before_atomic(); > - clear_bit(NFS4DS_CONNECTING, &ds->ds_state); > - smp_mb__after_atomic(); > - wake_up_bit(&ds->ds_state, NFS4DS_CONNECTING); > + clear_and_wake_up_bit(NFS4DS_CONNECTING, &ds->ds_state); > } > > static struct nfs_client *(*get_v3_ds_connect)( > diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c > index 87679557d0d6..0a30f9cdf66a 100644 > --- a/fs/nfsd/nfs4recover.c > +++ b/fs/nfsd/nfs4recover.c > @@ -1638,9 +1638,7 @@ static void > nfsd4_cltrack_upcall_unlock(struct nfs4_client *clp) > { > smp_mb__before_atomic(); > - clear_bit(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK); > + clear_and_wake_up_bit(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags); > } > > static void > diff --git a/fs/orangefs/file.c b/fs/orangefs/file.c > index a35c17017210..1958bb457143 100644 > --- a/fs/orangefs/file.c > +++ b/fs/orangefs/file.c > @@ -302,7 +302,7 @@ int orangefs_revalidate_mapping(struct inode *inode) > orangefs_inode->mapping_time = jiffies + > orangefs_cache_timeout_msecs*HZ/1000; > > - clear_bit(1, bitlock); > + clear_bit_unlock(1, bitlock); > smp_mb__after_atomic(); > wake_up_bit(bitlock, 1); > > diff --git a/kernel/sched/wait_bit.c b/kernel/sched/wait_bit.c > index 45eba18a2898..2662975473e3 100644 > --- a/kernel/sched/wait_bit.c > +++ b/kernel/sched/wait_bit.c > @@ -189,6 +189,7 @@ EXPORT_SYMBOL(init_wait_var_entry); > > void wake_up_var(void *var) > { > + smp_mb(); > __wake_up_bit(__var_waitqueue(var), var, -1); > } > EXPORT_SYMBOL(wake_up_var); > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > index 9e4fcf406d9c..4e57f1a1b7a2 100644 > --- a/net/bluetooth/hci_event.c > +++ b/net/bluetooth/hci_event.c > @@ -50,9 +50,7 @@ static void hci_cc_inquiry_cancel(struct hci_dev *hdev, struct sk_buff *skb) > if (status) > return; > > - clear_bit(HCI_INQUIRY, &hdev->flags); > - smp_mb__after_atomic(); /* wake_up_bit advises about this barrier */ > - wake_up_bit(&hdev->flags, HCI_INQUIRY); > + clear_and_wake_up_bit(HCI_INQUIRY, &hdev->flags); > > hci_dev_lock(hdev); > /* Set discovery state to stopped if we're not doing LE active > @@ -2342,7 +2340,6 @@ static void hci_inquiry_complete_evt(struct hci_dev *hdev, struct sk_buff *skb) > if (!test_and_clear_bit(HCI_INQUIRY, &hdev->flags)) > return; > > - smp_mb__after_atomic(); /* wake_up_bit advises about this barrier */ > wake_up_bit(&hdev->flags, HCI_INQUIRY); > > if (!hci_dev_test_flag(hdev, HCI_MGMT)) > diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c > index 3cae88cbdaa0..2c2773172964 100644 > --- a/net/rds/ib_recv.c > +++ b/net/rds/ib_recv.c > @@ -363,6 +363,7 @@ static int acquire_refill(struct rds_connection *conn) > static void release_refill(struct rds_connection *conn) > { > clear_bit(RDS_RECV_REFILL, &conn->c_flags); > + smp_mb__after_atomic(); > > /* We don't use wait_on_bit()/wake_up_bit() because our waking is in a > * hot path and finding waiters is very rare. We don't want to walk > diff --git a/security/keys/gc.c b/security/keys/gc.c > index 44e58a3e5663..f452816bd7d0 100644 > --- a/security/keys/gc.c > +++ b/security/keys/gc.c > @@ -308,9 +308,8 @@ static void key_garbage_collector(struct work_struct *work) > > if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) { > kdebug("dead wake"); > - smp_mb(); > - clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); > - wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE); > + smp_mb__before_atomic(); > + clear_and_wake_up_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); > } > > if (gc_state & KEY_GC_REAP_AGAIN) Thanks, Andreas -- To unsubscribe, send a message with 'unsubscribe linux-aio' in the body to majordomo@kvack.org. For more info on Linux AIO, see: http://www.kvack.org/aio/ Don't email: aart@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Gruenbacher Date: Tue, 25 Jun 2019 11:19:35 +0200 Subject: [Cluster-devel] [RFC][PATCH] wake_up_var() memory ordering In-Reply-To: <20190624165012.GH3436@hirez.programming.kicks-ass.net> References: <20190624165012.GH3436@hirez.programming.kicks-ass.net> Message-ID: List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Peter, thanks for the fixes. On Mon, 24 Jun 2019 at 18:53, Peter Zijlstra wrote: > Hi all, > > I tried using wake_up_var() today and accidentally noticed that it > didn't imply an smp_mb() and specifically requires it through > wake_up_bit() / waitqueue_active(). > > Now, wake_up_bit() doesn't imply the barrier because it is assumed to be > used with the atomic bitops API which either implies (test_and_clear) or > only needs smp_mb__after_atomic(), which is 'much' cheaper than an > unconditional smp_mb(). > > Still, while auditing all that, I found a whole bunch of things that > could be improved. There were missing barriers, superfluous barriers and > a whole bunch of sites that could use clear_and_wake_up_bit(). > > So this fixes all wake_up_bit() usage without actually changing > semantics of it (which are unfortunate but understandable). thanks for the fixes. > This does > however change the semantics of wake_up_var(); even though wake_up_var() > is most often used with atomics and then the additional smp_mb() is most > often superfluous :/ > > There isn't really a good option here, comments (other than I need to > split this up)? > > > --- > drivers/bluetooth/btmtksdio.c | 5 +---- > drivers/bluetooth/btmtkuart.c | 5 +---- > drivers/bluetooth/hci_mrvl.c | 8 ++------ > drivers/gpu/drm/i915/i915_reset.c | 6 ++---- > drivers/md/dm-bufio.c | 10 ++-------- > drivers/media/usb/dvb-usb-v2/dvb_usb_core.c | 15 ++++----------- > fs/afs/fs_probe.c | 1 + > fs/afs/server.c | 1 + > fs/afs/vl_probe.c | 1 + > fs/afs/volume.c | 1 + > fs/aio.c | 4 +--- > fs/block_dev.c | 1 + > fs/btrfs/extent_io.c | 4 +--- > fs/cachefiles/namei.c | 1 + > fs/cifs/connect.c | 3 +-- > fs/cifs/misc.c | 15 +++++---------- > fs/fscache/cookie.c | 2 ++ > fs/fscache/object.c | 2 ++ > fs/fscache/page.c | 3 +++ > fs/gfs2/glock.c | 8 ++------ > fs/gfs2/glops.c | 1 + > fs/gfs2/lock_dlm.c | 8 ++------ > fs/gfs2/recovery.c | 4 +--- > fs/gfs2/super.c | 1 + > fs/gfs2/sys.c | 4 +--- > fs/nfs/nfs4state.c | 4 +--- > fs/nfs/pnfs_nfs.c | 4 +--- > fs/nfsd/nfs4recover.c | 4 +--- > fs/orangefs/file.c | 2 +- > kernel/sched/wait_bit.c | 1 + > net/bluetooth/hci_event.c | 5 +---- > net/rds/ib_recv.c | 1 + > security/keys/gc.c | 5 ++--- > 33 files changed, 50 insertions(+), 90 deletions(-) > > diff --git a/drivers/bluetooth/btmtksdio.c b/drivers/bluetooth/btmtksdio.c > index 813338288453..27523cfeac9a 100644 > --- a/drivers/bluetooth/btmtksdio.c > +++ b/drivers/bluetooth/btmtksdio.c > @@ -356,11 +356,8 @@ static int btmtksdio_recv_event(struct hci_dev *hdev, struct sk_buff *skb) > > if (hdr->evt == HCI_EV_VENDOR) { > if (test_and_clear_bit(BTMTKSDIO_TX_WAIT_VND_EVT, > - &bdev->tx_state)) { > - /* Barrier to sync with other CPUs */ > - smp_mb__after_atomic(); > + &bdev->tx_state)) > wake_up_bit(&bdev->tx_state, BTMTKSDIO_TX_WAIT_VND_EVT); > - } > } > > return 0; > diff --git a/drivers/bluetooth/btmtkuart.c b/drivers/bluetooth/btmtkuart.c > index f5dbeec8e274..7fe324df3799 100644 > --- a/drivers/bluetooth/btmtkuart.c > +++ b/drivers/bluetooth/btmtkuart.c > @@ -340,11 +340,8 @@ static int btmtkuart_recv_event(struct hci_dev *hdev, struct sk_buff *skb) > > if (hdr->evt == HCI_EV_VENDOR) { > if (test_and_clear_bit(BTMTKUART_TX_WAIT_VND_EVT, > - &bdev->tx_state)) { > - /* Barrier to sync with other CPUs */ > - smp_mb__after_atomic(); > + &bdev->tx_state)) > wake_up_bit(&bdev->tx_state, BTMTKUART_TX_WAIT_VND_EVT); > - } > } > > return 0; > diff --git a/drivers/bluetooth/hci_mrvl.c b/drivers/bluetooth/hci_mrvl.c > index 50212ac629e3..f03294d39d08 100644 > --- a/drivers/bluetooth/hci_mrvl.c > +++ b/drivers/bluetooth/hci_mrvl.c > @@ -157,9 +157,7 @@ static int mrvl_recv_fw_req(struct hci_dev *hdev, struct sk_buff *skb) > > mrvl->tx_len = le16_to_cpu(pkt->lhs); > > - clear_bit(STATE_FW_REQ_PENDING, &mrvl->flags); > - smp_mb__after_atomic(); > - wake_up_bit(&mrvl->flags, STATE_FW_REQ_PENDING); > + clear_and_wake_up_bit(STATE_FW_REQ_PENDING, &mrvl->flags); > > done: > kfree_skb(skb); > @@ -192,9 +190,7 @@ static int mrvl_recv_chip_ver(struct hci_dev *hdev, struct sk_buff *skb) > > bt_dev_info(hdev, "Controller id = %x, rev = %x", mrvl->id, mrvl->rev); > > - clear_bit(STATE_CHIP_VER_PENDING, &mrvl->flags); > - smp_mb__after_atomic(); > - wake_up_bit(&mrvl->flags, STATE_CHIP_VER_PENDING); > + clear_and_wake_up_bit(STATE_CHIP_VER_PENDING, &mrvl->flags); > > done: > kfree_skb(skb); > diff --git a/drivers/gpu/drm/i915/i915_reset.c b/drivers/gpu/drm/i915/i915_reset.c > index 677d59304e78..6809367dbfa9 100644 > --- a/drivers/gpu/drm/i915/i915_reset.c > +++ b/drivers/gpu/drm/i915/i915_reset.c > @@ -1324,10 +1324,8 @@ void i915_handle_error(struct drm_i915_private *i915, > if (i915_reset_engine(engine, msg) == 0) > engine_mask &= ~engine->mask; > > - clear_bit(I915_RESET_ENGINE + engine->id, > - &error->flags); > - wake_up_bit(&error->flags, > - I915_RESET_ENGINE + engine->id); > + clear_and_wake_up_bit(I915_RESET_ENGINE + engine->id, > + &error->flags); > } > } > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > index 2a48ea3f1b30..3114836cc717 100644 > --- a/drivers/md/dm-bufio.c > +++ b/drivers/md/dm-bufio.c > @@ -667,10 +667,7 @@ static void write_endio(struct dm_buffer *b, blk_status_t status) > BUG_ON(!test_bit(B_WRITING, &b->state)); > > smp_mb__before_atomic(); > - clear_bit(B_WRITING, &b->state); > - smp_mb__after_atomic(); > - > - wake_up_bit(&b->state, B_WRITING); > + clear_and_wake_up_bit(B_WRITING, &b->state); > } > > /* > @@ -1045,10 +1042,7 @@ static void read_endio(struct dm_buffer *b, blk_status_t status) > BUG_ON(!test_bit(B_READING, &b->state)); > > smp_mb__before_atomic(); > - clear_bit(B_READING, &b->state); > - smp_mb__after_atomic(); > - > - wake_up_bit(&b->state, B_READING); > + clear_and_wake_up_bit(B_READING, &b->state); > } > > /* > diff --git a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c > index e5e056bf9dfa..fa46bc930704 100644 > --- a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c > +++ b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c > @@ -374,9 +374,7 @@ static int dvb_usb_stop_feed(struct dvb_demux_feed *dvbdmxfeed) > usb_urb_killv2(&adap->stream); > > /* clear 'streaming' status bit */ > - clear_bit(ADAP_STREAMING, &adap->state_bits); > - smp_mb__after_atomic(); > - wake_up_bit(&adap->state_bits, ADAP_STREAMING); > + clear_and_wake_up_bit(ADAP_STREAMING, &adap->state_bits); > skip_feed_stop: > > if (ret) > @@ -578,11 +576,8 @@ static int dvb_usb_fe_init(struct dvb_frontend *fe) > goto err; > } > err: > - if (!adap->suspend_resume_active) { > - clear_bit(ADAP_INIT, &adap->state_bits); > - smp_mb__after_atomic(); > - wake_up_bit(&adap->state_bits, ADAP_INIT); > - } > + if (!adap->suspend_resume_active) > + clear_and_wake_up_bit(ADAP_INIT, &adap->state_bits); > > dev_dbg(&d->udev->dev, "%s: ret=%d\n", __func__, ret); > return ret; > @@ -619,9 +614,7 @@ static int dvb_usb_fe_sleep(struct dvb_frontend *fe) > err: > if (!adap->suspend_resume_active) { > adap->active_fe = -1; > - clear_bit(ADAP_SLEEP, &adap->state_bits); > - smp_mb__after_atomic(); > - wake_up_bit(&adap->state_bits, ADAP_SLEEP); > + clear_and_wake_up_bit(ADAP_SLEEP, &adap->state_bits); > } > > dev_dbg(&d->udev->dev, "%s: ret=%d\n", __func__, ret); > diff --git a/fs/afs/fs_probe.c b/fs/afs/fs_probe.c > index cfe62b154f68..377ee07d5f76 100644 > --- a/fs/afs/fs_probe.c > +++ b/fs/afs/fs_probe.c > @@ -18,6 +18,7 @@ static bool afs_fs_probe_done(struct afs_server *server) > > wake_up_var(&server->probe_outstanding); > clear_bit_unlock(AFS_SERVER_FL_PROBING, &server->flags); > + smp_mb__after_atomic(); > wake_up_bit(&server->flags, AFS_SERVER_FL_PROBING); > return true; > } > diff --git a/fs/afs/server.c b/fs/afs/server.c > index e900cd74361b..c9b74a397cc1 100644 > --- a/fs/afs/server.c > +++ b/fs/afs/server.c > @@ -569,6 +569,7 @@ bool afs_check_server_record(struct afs_fs_cursor *fc, struct afs_server *server > if (!test_and_set_bit_lock(AFS_SERVER_FL_UPDATING, &server->flags)) { > success = afs_update_server_record(fc, server); > clear_bit_unlock(AFS_SERVER_FL_UPDATING, &server->flags); > + smp_mb__after_atomic(); > wake_up_bit(&server->flags, AFS_SERVER_FL_UPDATING); > _leave(" = %d", success); > return success; > diff --git a/fs/afs/vl_probe.c b/fs/afs/vl_probe.c > index 858498cc1b05..1939624aa147 100644 > --- a/fs/afs/vl_probe.c > +++ b/fs/afs/vl_probe.c > @@ -18,6 +18,7 @@ static bool afs_vl_probe_done(struct afs_vlserver *server) > > wake_up_var(&server->probe_outstanding); > clear_bit_unlock(AFS_VLSERVER_FL_PROBING, &server->flags); > + smp_mb__after_atomic(); > wake_up_bit(&server->flags, AFS_VLSERVER_FL_PROBING); > return true; > } > diff --git a/fs/afs/volume.c b/fs/afs/volume.c > index 08fdb3951c49..b968e4e96f6b 100644 > --- a/fs/afs/volume.c > +++ b/fs/afs/volume.c > @@ -303,6 +303,7 @@ int afs_check_volume_status(struct afs_volume *volume, struct key *key) > ret = afs_update_volume_status(volume, key); > clear_bit_unlock(AFS_VOLUME_WAIT, &volume->flags); > clear_bit_unlock(AFS_VOLUME_UPDATING, &volume->flags); > + smp_mb__after_atomic(); > wake_up_bit(&volume->flags, AFS_VOLUME_WAIT); > _leave(" = %d", ret); > return ret; > diff --git a/fs/aio.c b/fs/aio.c > index 3490d1fa0e16..a21acb7ee2a5 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -1154,9 +1154,7 @@ static void aio_complete(struct aio_kiocb *iocb) > * like in wake_up_bit() where clearing a bit has to be > * ordered with the unlocked test. > */ > - smp_mb(); > - > - if (waitqueue_active(&ctx->wait)) > + if (wq_has_sleeper(&ctx->wait)) > wake_up(&ctx->wait); > } > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 749f5984425d..80e35cbfc7cc 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -1687,6 +1687,7 @@ int blkdev_get(struct block_device *bdev, fmode_t mode, void *holder) > /* tell others that we're done */ > BUG_ON(whole->bd_claiming != holder); > whole->bd_claiming = NULL; > + smp_mb(); > wake_up_bit(&whole->bd_claiming, 0); > > spin_unlock(&bdev_lock); > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index db337e53aab3..ee1136ae46fd 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -3683,9 +3683,7 @@ static noinline_for_stack int lock_extent_buffer_for_io(struct extent_buffer *eb > > static void end_extent_buffer_writeback(struct extent_buffer *eb) > { > - clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags); > - smp_mb__after_atomic(); > - wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK); > + clear_and_wake_up_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags); > } > > static void set_btree_ioerr(struct page *page) > diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c > index ecc8ecbbfa5a..ecebba72ec7d 100644 > --- a/fs/cachefiles/namei.c > +++ b/fs/cachefiles/namei.c > @@ -267,6 +267,7 @@ void cachefiles_mark_object_inactive(struct cachefiles_cache *cache, > clear_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags); > write_unlock(&cache->active_lock); > > + smp_mb__after_atomic(); > wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE); > > /* This object can now be culled, so we need to let the daemon know > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c > index 8c4121da624e..8c1115ed1c28 100644 > --- a/fs/cifs/connect.c > +++ b/fs/cifs/connect.c > @@ -5235,8 +5235,7 @@ cifs_sb_tlink(struct cifs_sb_info *cifs_sb) > } > > tlink->tl_tcon = cifs_construct_tcon(cifs_sb, fsuid); > - clear_bit(TCON_LINK_PENDING, &tlink->tl_flags); > - wake_up_bit(&tlink->tl_flags, TCON_LINK_PENDING); > + clear_and_wake_up_bit(TCON_LINK_PENDING, &tlink->tl_flags); > > if (IS_ERR(tlink->tl_tcon)) { > cifs_put_tlink(tlink); > diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c > index b1a696a73f7c..961751d89113 100644 > --- a/fs/cifs/misc.c > +++ b/fs/cifs/misc.c > @@ -584,10 +584,8 @@ int cifs_get_writer(struct cifsInodeInfo *cinode) > /* Check to see if we have started servicing an oplock break */ > if (test_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags)) { > cinode->writers--; > - if (cinode->writers == 0) { > - clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > - wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); > - } > + if (cinode->writers == 0) > + clear_and_wake_up_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > spin_unlock(&cinode->writers_lock); > goto start; > } > @@ -599,10 +597,8 @@ void cifs_put_writer(struct cifsInodeInfo *cinode) > { > spin_lock(&cinode->writers_lock); > cinode->writers--; > - if (cinode->writers == 0) { > - clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > - wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS); > - } > + if (cinode->writers == 0) > + clear_and_wake_up_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags); > spin_unlock(&cinode->writers_lock); > } > > @@ -630,8 +626,7 @@ void cifs_queue_oplock_break(struct cifsFileInfo *cfile) > > void cifs_done_oplock_break(struct cifsInodeInfo *cinode) > { > - clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags); > - wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK); > + clear_and_wake_up_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags); > } > > bool > diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c > index 0ce39658a620..40ba8957ebf0 100644 > --- a/fs/fscache/cookie.c > +++ b/fs/fscache/cookie.c > @@ -381,6 +381,7 @@ void __fscache_enable_cookie(struct fscache_cookie *cookie, > > out_unlock: > clear_bit_unlock(FSCACHE_COOKIE_ENABLEMENT_LOCK, &cookie->flags); > + smp_mb__after_atomic(); > wake_up_bit(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK); > } > EXPORT_SYMBOL(__fscache_enable_cookie); > @@ -778,6 +779,7 @@ void __fscache_disable_cookie(struct fscache_cookie *cookie, > > out_unlock_enable: > clear_bit_unlock(FSCACHE_COOKIE_ENABLEMENT_LOCK, &cookie->flags); > + smp_mb__after_atomic(); > wake_up_bit(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK); > _leave(""); > } > diff --git a/fs/fscache/object.c b/fs/fscache/object.c > index cfeba839a0f2..08b2edec6596 100644 > --- a/fs/fscache/object.c > +++ b/fs/fscache/object.c > @@ -524,6 +524,7 @@ void fscache_object_lookup_negative(struct fscache_object *object) > > _debug("wake up lookup %p", &cookie->flags); > clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags); > + smp_mb__after_atomic(); > wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP); > } > _leave(""); > @@ -559,6 +560,7 @@ void fscache_obtained_object(struct fscache_object *object) > * to begin shovelling data. > */ > clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags); > + smp_mb__after_atomic(); > wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP); > } else { > fscache_stat(&fscache_n_object_created); > diff --git a/fs/fscache/page.c b/fs/fscache/page.c > index 26af6fdf1538..49ef238502a3 100644 > --- a/fs/fscache/page.c > +++ b/fs/fscache/page.c > @@ -113,6 +113,7 @@ bool __fscache_maybe_release_page(struct fscache_cookie *cookie, > fscache_stat(&fscache_n_store_vmscan_gone); > } > > + smp_mb(); > wake_up_bit(&cookie->flags, 0); > trace_fscache_wake_cookie(cookie); > if (xpage) > @@ -171,6 +172,7 @@ static void fscache_end_page_write(struct fscache_object *object, > trace_fscache_page(cookie, page, fscache_page_write_end_pend); > } > spin_unlock(&cookie->stores_lock); > + smp_mb(); > wake_up_bit(&cookie->flags, 0); > trace_fscache_wake_cookie(cookie); > } else { > @@ -922,6 +924,7 @@ void fscache_invalidate_writes(struct fscache_cookie *cookie) > put_page(results[i]); > } > > + smp_mb(); > wake_up_bit(&cookie->flags, 0); > trace_fscache_wake_cookie(cookie); > > diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c > index f1ebcb42cbf5..8024b6bdb6d4 100644 > --- a/fs/gfs2/glock.c > +++ b/fs/gfs2/glock.c > @@ -302,9 +302,7 @@ static inline int may_grant(const struct gfs2_glock *gl, const struct gfs2_holde > > static void gfs2_holder_wake(struct gfs2_holder *gh) > { > - clear_bit(HIF_WAIT, &gh->gh_iflags); > - smp_mb__after_atomic(); > - wake_up_bit(&gh->gh_iflags, HIF_WAIT); > + clear_and_wake_up_bit(HIF_WAIT, &gh->gh_iflags); > } > > /** > @@ -436,9 +434,7 @@ static void state_change(struct gfs2_glock *gl, unsigned int new_state) > static void gfs2_demote_wake(struct gfs2_glock *gl) > { > gl->gl_demote_state = LM_ST_EXCLUSIVE; > - clear_bit(GLF_DEMOTE, &gl->gl_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&gl->gl_flags, GLF_DEMOTE); > + clear_and_wake_up_bit(GLF_DEMOTE, &gl->gl_flags); > } > > /** > diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c > index cf4c767005b1..666629ea5da7 100644 > --- a/fs/gfs2/glops.c > +++ b/fs/gfs2/glops.c > @@ -227,6 +227,7 @@ static void gfs2_clear_glop_pending(struct gfs2_inode *ip) > return; > > clear_bit_unlock(GIF_GLOP_PENDING, &ip->i_flags); > + smp_mb__after_atomic(); > wake_up_bit(&ip->i_flags, GIF_GLOP_PENDING); This should become clear_and_wake_up_bit as well, right? There are several more instances of the same pattern. > } > > diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c > index 4361804646d8..0fa1865dd600 100644 > --- a/fs/gfs2/lock_dlm.c > +++ b/fs/gfs2/lock_dlm.c > @@ -1139,9 +1139,7 @@ static void gdlm_recover_done(void *arg, struct dlm_slot *slots, int num_slots, > if (!test_bit(DFL_UNMOUNT, &ls->ls_recover_flags)) > queue_delayed_work(gfs2_control_wq, &sdp->sd_control_work, 0); > > - clear_bit(DFL_DLM_RECOVERY, &ls->ls_recover_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&ls->ls_recover_flags, DFL_DLM_RECOVERY); > + clear_and_wake_up_bit(DFL_DLM_RECOVERY, &ls->ls_recover_flags); > spin_unlock(&ls->ls_recover_spin); > } > > @@ -1276,9 +1274,7 @@ static int gdlm_mount(struct gfs2_sbd *sdp, const char *table) > } > > ls->ls_first = !!test_bit(DFL_FIRST_MOUNT, &ls->ls_recover_flags); > - clear_bit(SDF_NOJOURNALID, &sdp->sd_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&sdp->sd_flags, SDF_NOJOURNALID); > + clear_and_wake_up_bit(SDF_NOJOURNALID, &sdp->sd_flags); > return 0; > > fail_release: > diff --git a/fs/gfs2/recovery.c b/fs/gfs2/recovery.c > index 2299a3fa1911..ef9a8ef6689b 100644 > --- a/fs/gfs2/recovery.c > +++ b/fs/gfs2/recovery.c > @@ -436,9 +436,7 @@ void gfs2_recover_func(struct work_struct *work) > jd->jd_recover_error = error; > gfs2_recovery_done(sdp, jd->jd_jid, LM_RD_GAVEUP); > done: > - clear_bit(JDF_RECOVERY, &jd->jd_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&jd->jd_flags, JDF_RECOVERY); > + clear_and_wake_up_bit(JDF_RECOVERY, &jd->jd_flags); > } > > int gfs2_recover_journal(struct gfs2_jdesc *jd, bool wait) > diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c > index b70cea5c8c59..28ff2e10bdd9 100644 > --- a/fs/gfs2/super.c > +++ b/fs/gfs2/super.c > @@ -985,6 +985,7 @@ void gfs2_freeze_func(struct work_struct *work) > } > deactivate_super(sb); > clear_bit_unlock(SDF_FS_FROZEN, &sdp->sd_flags); > + smp_mb__after_atomic(); > wake_up_bit(&sdp->sd_flags, SDF_FS_FROZEN); > return; > } > diff --git a/fs/gfs2/sys.c b/fs/gfs2/sys.c > index 159aedf63c2a..b337798d8957 100644 > --- a/fs/gfs2/sys.c > +++ b/fs/gfs2/sys.c > @@ -505,9 +505,7 @@ static ssize_t jid_store(struct gfs2_sbd *sdp, const char *buf, size_t len) > if (sdp->sd_args.ar_spectator && jid > 0) > rv = jid = -EINVAL; > sdp->sd_lockstruct.ls_jid = jid; > - clear_bit(SDF_NOJOURNALID, &sdp->sd_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&sdp->sd_flags, SDF_NOJOURNALID); > + clear_and_wake_up_bit(SDF_NOJOURNALID, &sdp->sd_flags); > out: > spin_unlock(&sdp->sd_jindex_spin); > return rv ? rv : len; > diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c > index e2e3c4f04d3e..a3ed413a38c5 100644 > --- a/fs/nfs/nfs4state.c > +++ b/fs/nfs/nfs4state.c > @@ -1196,9 +1196,7 @@ static int nfs4_run_state_manager(void *); > static void nfs4_clear_state_manager_bit(struct nfs_client *clp) > { > smp_mb__before_atomic(); > - clear_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state); > - smp_mb__after_atomic(); > - wake_up_bit(&clp->cl_state, NFS4CLNT_MANAGER_RUNNING); > + clear_and_wake_up_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state); > rpc_wake_up(&clp->cl_rpcwaitq); > } > > diff --git a/fs/nfs/pnfs_nfs.c b/fs/nfs/pnfs_nfs.c > index c0046c348910..37c4fe5a595c 100644 > --- a/fs/nfs/pnfs_nfs.c > +++ b/fs/nfs/pnfs_nfs.c > @@ -567,9 +567,7 @@ static void nfs4_wait_ds_connect(struct nfs4_pnfs_ds *ds) > static void nfs4_clear_ds_conn_bit(struct nfs4_pnfs_ds *ds) > { > smp_mb__before_atomic(); > - clear_bit(NFS4DS_CONNECTING, &ds->ds_state); > - smp_mb__after_atomic(); > - wake_up_bit(&ds->ds_state, NFS4DS_CONNECTING); > + clear_and_wake_up_bit(NFS4DS_CONNECTING, &ds->ds_state); > } > > static struct nfs_client *(*get_v3_ds_connect)( > diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c > index 87679557d0d6..0a30f9cdf66a 100644 > --- a/fs/nfsd/nfs4recover.c > +++ b/fs/nfsd/nfs4recover.c > @@ -1638,9 +1638,7 @@ static void > nfsd4_cltrack_upcall_unlock(struct nfs4_client *clp) > { > smp_mb__before_atomic(); > - clear_bit(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags); > - smp_mb__after_atomic(); > - wake_up_bit(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK); > + clear_and_wake_up_bit(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags); > } > > static void > diff --git a/fs/orangefs/file.c b/fs/orangefs/file.c > index a35c17017210..1958bb457143 100644 > --- a/fs/orangefs/file.c > +++ b/fs/orangefs/file.c > @@ -302,7 +302,7 @@ int orangefs_revalidate_mapping(struct inode *inode) > orangefs_inode->mapping_time = jiffies + > orangefs_cache_timeout_msecs*HZ/1000; > > - clear_bit(1, bitlock); > + clear_bit_unlock(1, bitlock); > smp_mb__after_atomic(); > wake_up_bit(bitlock, 1); > > diff --git a/kernel/sched/wait_bit.c b/kernel/sched/wait_bit.c > index 45eba18a2898..2662975473e3 100644 > --- a/kernel/sched/wait_bit.c > +++ b/kernel/sched/wait_bit.c > @@ -189,6 +189,7 @@ EXPORT_SYMBOL(init_wait_var_entry); > > void wake_up_var(void *var) > { > + smp_mb(); > __wake_up_bit(__var_waitqueue(var), var, -1); > } > EXPORT_SYMBOL(wake_up_var); > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c > index 9e4fcf406d9c..4e57f1a1b7a2 100644 > --- a/net/bluetooth/hci_event.c > +++ b/net/bluetooth/hci_event.c > @@ -50,9 +50,7 @@ static void hci_cc_inquiry_cancel(struct hci_dev *hdev, struct sk_buff *skb) > if (status) > return; > > - clear_bit(HCI_INQUIRY, &hdev->flags); > - smp_mb__after_atomic(); /* wake_up_bit advises about this barrier */ > - wake_up_bit(&hdev->flags, HCI_INQUIRY); > + clear_and_wake_up_bit(HCI_INQUIRY, &hdev->flags); > > hci_dev_lock(hdev); > /* Set discovery state to stopped if we're not doing LE active > @@ -2342,7 +2340,6 @@ static void hci_inquiry_complete_evt(struct hci_dev *hdev, struct sk_buff *skb) > if (!test_and_clear_bit(HCI_INQUIRY, &hdev->flags)) > return; > > - smp_mb__after_atomic(); /* wake_up_bit advises about this barrier */ > wake_up_bit(&hdev->flags, HCI_INQUIRY); > > if (!hci_dev_test_flag(hdev, HCI_MGMT)) > diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c > index 3cae88cbdaa0..2c2773172964 100644 > --- a/net/rds/ib_recv.c > +++ b/net/rds/ib_recv.c > @@ -363,6 +363,7 @@ static int acquire_refill(struct rds_connection *conn) > static void release_refill(struct rds_connection *conn) > { > clear_bit(RDS_RECV_REFILL, &conn->c_flags); > + smp_mb__after_atomic(); > > /* We don't use wait_on_bit()/wake_up_bit() because our waking is in a > * hot path and finding waiters is very rare. We don't want to walk > diff --git a/security/keys/gc.c b/security/keys/gc.c > index 44e58a3e5663..f452816bd7d0 100644 > --- a/security/keys/gc.c > +++ b/security/keys/gc.c > @@ -308,9 +308,8 @@ static void key_garbage_collector(struct work_struct *work) > > if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) { > kdebug("dead wake"); > - smp_mb(); > - clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); > - wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE); > + smp_mb__before_atomic(); > + clear_and_wake_up_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); > } > > if (gc_state & KEY_GC_REAP_AGAIN) Thanks, Andreas