From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> Subject: Re: bsg locking patches update Date: Wed, 28 May 2008 21:00:56 +0900 > On Mon, 26 May 2008 12:53:18 -0400 > Pete Wyckoff <pw@xxxxxxx> wrote: > > > I finally got around to testing the set of lifetime management > > fixes you applied. This is 2.6.26-rc3 with some varlen, bidi, > > iser patches, and iovec on bsg, but nothing that should affect > > the locking. > > > > I can confirm that the first two of these three old bugs are > > no longer reproducable: > > > > http://marc.info/?l=linux-scsi&m=120508166505141&w=2 > > http://marc.info/?l=linux-scsi&m=120508177905365&w=2 > > http://marc.info/?l=linux-scsi&m=120508178005376&w=2 > > > > Thanks! The third, however, is a hang that still can happen. But > > it is very obscure and requires a bit of timing to get right. As a > > reminder, here's the setup, and updated traces. > > Ah, sorry about it. I didn't understand the third correctly. > > > > Maybe it is necessary to split up that bsg_mutex to use multiple > > finer-grained locks. > > We could but we use bsg_mutex to protect bsg_device_list and idr. So I > think that we don't need hold bsg_mutex during > bsg_complete_all_commands. How about this? > > > diff --git a/block/bsg.c b/block/bsg.c > index f0b7cd3..d81104e 100644 > --- a/block/bsg.c > +++ b/block/bsg.c On second thoughts, I realized that the previous patch leads to a race between bsg_put_device and __bsg_get_device (__bsg_get_device possibly finds a device that is being removed). Here's new one. diff --git a/block/bsg.c b/block/bsg.c index f0b7cd3..7cdec32 100644 --- a/block/bsg.c +++ b/block/bsg.c @@ -724,8 +724,13 @@ static int bsg_put_device(struct bsg_device *bd) mutex_lock(&bsg_mutex); do_free = atomic_dec_and_test(&bd->ref_count); - if (!do_free) + if (!do_free) { + mutex_unlock(&bsg_mutex); goto out; + } + + hlist_del(&bd->dev_list); + mutex_unlock(&bsg_mutex); dprintk("%s: tearing down\n", bd->name); @@ -741,10 +746,8 @@ static int bsg_put_device(struct bsg_device *bd) */ ret = bsg_complete_all_commands(bd); - hlist_del(&bd->dev_list); kfree(bd); out: - mutex_unlock(&bsg_mutex); kref_put(&q->bsg_dev.ref, bsg_kref_release_function); if (do_free) blk_put_queue(q); -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
