On 09/19/2014 05:38 AM, Christoph Hellwig wrote: > Hi Jens, hi Tejun, > > I've seen multi-second boot stalls in one of my KVM setups during > the initial scsi scan: > > [ 0.949892] scsi host0: Virtio SCSI HBA > [ 1.007864] scsi 0:0:0:0: Direct-Access QEMU QEMU HARDDISK 1.1. PQ: 0 ANSI: 5 > [ 1.021299] scsi 0:0:1:0: Direct-Access QEMU QEMU HARDDISK 1.1. PQ: 0 ANSI: 5 > [ 1.520356] tsc: Refined TSC clocksource calibration: 2491.910 MHz > > <stall> > > [ 16.186549] sd 0:0:0:0: Attached scsi generic sg0 type 0 > [ 16.190478] sd 0:0:1:0: Attached scsi generic sg1 type 0 > [ 16.194099] osd: LOADED open-osd 0.2.1 > [ 16.203202] sd 0:0:0:0: [sda] 31457280 512-byte logical blocks: (16.1 GB/15.0 GiB) > [ 16.208478] sd 0:0:0:0: [sda] Write Protect is off > [ 16.211439] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA > [ 16.218771] sd 0:0:1:0: [sdb] 31457280 512-byte logical blocks: (16.1 GB/15.0 GiB) > [ 16.223264] sd 0:0:1:0: [sdb] Write Protect is off > [ 16.225682] sd 0:0:1:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA > > > > I've tracked this down to "blk-mq: use percpu_ref for mq usage count" in > a rather painful way as that one introduced enough other regressions > to mess up bisect. > > If I revert the following commits: > > dd840087086f3b93ac20f7472b4fca59aff7b79f > cddd5d17642cc6881352732693c2ae6930e9ce65 > add703fda981b9719d37f371498b9f129acbd997 > > which are the above mentioned commit and two fixes to it the problem goes > away. Thanks for bisecting this, I ran into something that I think is the same issue about a week ago. Tejun, any ideas before I dig into this one? -- Jens Axboe -- 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
