linux-kernel - Re: boot stall regression due to blk-mq: use percpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <541C8047.80705@kernel.dk>
Date:	Fri, 19 Sep 2014 13:13:11 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Christoph Hellwig <hch@....de>, Tejun Heo <tj@...nel.org>
CC:	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Subject: Re: boot stall regression due to blk-mq: use percpu_ref for mq usage
 count

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-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/