From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: [patch 01/10 v3] raid5: use wake_up_all for overlap waking Date: Thu, 28 Jun 2012 17:26:21 +1000 Message-ID: <20120628172621.463d9a84@notabene.brown> References: <20120625072447.268095276@kernel.org> <20120625072553.970838108@kernel.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/hvCYd09_irsp5D4M6TGQ72p"; protocol="application/pgp-signature" Return-path: In-Reply-To: <20120625072553.970838108@kernel.org> Sender: linux-raid-owner@vger.kernel.org To: Shaohua Li Cc: linux-raid@vger.kernel.org, axboe@kernel.dk, dan.j.williams@intel.com, shli@fusionio.com List-Id: linux-raid.ids --Sig_/hvCYd09_irsp5D4M6TGQ72p Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Mon, 25 Jun 2012 15:24:48 +0800 Shaohua Li wrote: > It's possible several tasks are waiting for stripe overlap. We clear R5_O= verlap > bit and wake_up, but wake_up just wakes one task. So if there are several= tasks > in the wait queue, some tasks will not be woken up even its strip R5_Over= lap > clear. The end result is tasks hang in make_request. >=20 > wake_up_all should not introduce performance issue here, since overlap ca= se is > rare. This is not necessary. wake_up_all is only different from wake_up if WQ_FLAG_EXCLUSIVE it set, e.g. by prepare_to_wait_exclusive. As we don't use an exclusive wait to wait on wait_for_overlap, there is no point in using wake_up_all, wake_up already wakes everything up. NeilBrown >=20 > Signed-off-by: Shaohua Li > --- > drivers/md/raid5.c | 20 ++++++++++---------- > 1 file changed, 10 insertions(+), 10 deletions(-) >=20 > Index: linux/drivers/md/raid5.c > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > --- linux.orig/drivers/md/raid5.c 2012-06-19 08:11:10.021688417 +0800 > +++ linux/drivers/md/raid5.c 2012-06-19 08:11:29.833439339 +0800 > @@ -1399,7 +1399,7 @@ static void __raid_run_ops(struct stripe > for (i =3D disks; i--; ) { > struct r5dev *dev =3D &sh->dev[i]; > if (test_and_clear_bit(R5_Overlap, &dev->flags)) > - wake_up(&sh->raid_conf->wait_for_overlap); > + wake_up_all(&sh->raid_conf->wait_for_overlap); > } > put_cpu(); > } > @@ -2436,7 +2436,7 @@ handle_failed_stripe(struct r5conf *conf > } > =20 > if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags)) > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > =20 > while (bi && bi->bi_sector < > sh->dev[i].sector + STRIPE_SECTORS) { > @@ -2474,7 +2474,7 @@ handle_failed_stripe(struct r5conf *conf > bi =3D sh->dev[i].toread; > sh->dev[i].toread =3D NULL; > if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags)) > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > if (bi) s->to_read--; > while (bi && bi->bi_sector < > sh->dev[i].sector + STRIPE_SECTORS) { > @@ -3572,7 +3572,7 @@ static void handle_stripe(struct stripe_ > } else if (s.expanded && !sh->reconstruct_state && s.locked =3D=3D 0) { > clear_bit(STRIPE_EXPAND_READY, &sh->state); > atomic_dec(&conf->reshape_stripes); > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > md_done_sync(conf->mddev, STRIPE_SECTORS, 1); > } > =20 > @@ -4249,7 +4249,7 @@ static sector_t reshape_request(struct m > spin_lock_irq(&conf->device_lock); > conf->reshape_safe =3D mddev->reshape_position; > spin_unlock_irq(&conf->device_lock); > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > sysfs_notify(&mddev->kobj, NULL, "sync_completed"); > } > =20 > @@ -4340,7 +4340,7 @@ static sector_t reshape_request(struct m > spin_lock_irq(&conf->device_lock); > conf->reshape_safe =3D mddev->reshape_position; > spin_unlock_irq(&conf->device_lock); > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > sysfs_notify(&mddev->kobj, NULL, "sync_completed"); > } > return reshape_sectors; > @@ -5718,7 +5718,7 @@ static void end_reshape(struct r5conf *c > smp_wmb(); > conf->reshape_progress =3D MaxSector; > spin_unlock_irq(&conf->device_lock); > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > =20 > /* read-ahead size must cover two whole stripes, which is > * 2 * (datadisks) * chunksize where 'n' is the number of raid devices > @@ -5776,7 +5776,7 @@ static void raid5_quiesce(struct mddev * > =20 > switch(state) { > case 2: /* resume for a suspend */ > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > break; > =20 > case 1: /* stop all writes */ > @@ -5792,14 +5792,14 @@ static void raid5_quiesce(struct mddev * > conf->quiesce =3D 1; > spin_unlock_irq(&conf->device_lock); > /* allow reshape to continue */ > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > break; > =20 > case 0: /* re-enable writes */ > spin_lock_irq(&conf->device_lock); > conf->quiesce =3D 0; > wake_up(&conf->wait_for_stripe); > - wake_up(&conf->wait_for_overlap); > + wake_up_all(&conf->wait_for_overlap); > spin_unlock_irq(&conf->device_lock); > break; > } --Sig_/hvCYd09_irsp5D4M6TGQ72p Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBT+wHHTnsnt1WYoG5AQJHnhAAjPKz+h37y6TQQfX+x2CHOtiuweT1XpIS nlD2ru8aYP9CqQ+WTR1xToYCSmbHEALlob5Swu5xmCxk1SZSf65mnP7iCzCVW0dq swf1DJs2jGz0eCxuU0grGc8eYwc72up7Stjr2C6fP6Kl/M6vCV/pTcGb4nhSODAY Zw9y8+kF3SqeXj2B5nL91hPgAVcagR3uN3XRoVBReXcXQ5SuTS9UsVgxG/gkrXFd a2PYFDZhlAh6QYoRhD4psOLgPOr3NhCD2GXbU9HiiFjYEnO9wPwnoBc+/0k0n3aA ES/I65wTMyxQT1XH0IHZ5oBiDhxvRZypmsL/huZKCAHqbcNW++RbrCM4ma3qUcwg yAoBTB6GnsRr+6bucHukiWZy/Ts+Ok3TUAS7WdyASSUKXuXAFlQ0pH1wO3P9mdJp wRz0k0q74UicwX2OzjeMgcr+EMiGO6GeLz9pCDxRE8zIMjOEi+YFpDH2K9StxFR8 MmSEE9eWk3xt0iQkETFRxiBCa2RBI0As3Ad6Qu8MWgggruC93ALbaS2uAtVoOdH2 WSahIS+0/853kgXvUsulWJ48UoX8JlnHrt/xAAtTA87HbDp0M56tDdQZYQ7Z7yN4 U2yV9FvlBzML2VQjn2NmsYRdVcvYIfkD9VZ3+CN0xOhKekMzA/Q2aVfuQsjGya2I V8iKbhOJTBE= =l105 -----END PGP SIGNATURE----- --Sig_/hvCYd09_irsp5D4M6TGQ72p--