• Takashi Iwai's avatar
    blk-mq: Fix uninitialized kobject at CPU hotplugging · 06a41a99
    Takashi Iwai authored
    When a CPU is hotplugged, the current blk-mq spews a warning like:
    
      kobject '(null)' (ffffe8ffffc8b5d8): tried to add an uninitialized object, something is seriously wrong.
      CPU: 1 PID: 1386 Comm: systemd-udevd Not tainted 3.18.0-rc7-2.g088d59b-default #1
      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_171129-lamiak 04/01/2014
       0000000000000000 0000000000000002 ffffffff81605f07 ffffe8ffffc8b5d8
       ffffffff8132c7a0 ffff88023341d370 0000000000000020 ffff8800bb05bd58
       ffff8800bb05bd08 000000000000a0a0 000000003f441940 0000000000000007
      Call Trace:
       [<ffffffff81005306>] dump_trace+0x86/0x330
       [<ffffffff81005644>] show_stack_log_lvl+0x94/0x170
       [<ffffffff81006d21>] show_stack+0x21/0x50
       [<ffffffff81605f07>] dump_stack+0x41/0x51
       [<ffffffff8132c7a0>] kobject_add+0xa0/0xb0
       [<ffffffff8130aee1>] blk_mq_register_hctx+0x91/0xb0
       [<ffffffff8130b82e>] blk_mq_sysfs_register+0x3e/0x60
       [<ffffffff81309298>] blk_mq_queue_reinit_notify+0xf8/0x190
       [<ffffffff8107cfdc>] notifier_call_chain+0x4c/0x70
       [<ffffffff8105fd23>] cpu_notify+0x23/0x50
       [<ffffffff81060037>] _cpu_up+0x157/0x170
       [<ffffffff810600d9>] cpu_up+0x89/0xb0
       [<ffffffff815fa5b5>] cpu_subsys_online+0x35/0x80
       [<ffffffff814323cd>] device_online+0x5d/0xa0
       [<ffffffff81432485>] online_store+0x75/0x80
       [<ffffffff81236a5a>] kernfs_fop_write+0xda/0x150
       [<ffffffff811c5532>] vfs_write+0xb2/0x1f0
       [<ffffffff811c5f42>] SyS_write+0x42/0xb0
       [<ffffffff8160c4ed>] system_call_fastpath+0x16/0x1b
       [<00007f0132fb24e0>] 0x7f0132fb24e0
    
    This is indeed because of an uninitialized kobject for blk_mq_ctx.
    The blk_mq_ctx kobjects are initialized in blk_mq_sysfs_init(), but it
    goes loop over hctx_for_each_ctx(), i.e. it initializes only for
    online CPUs.  Thus, when a CPU is hotplugged, the ctx for the newly
    onlined CPU is registered without initialization.
    
    This patch fixes the issue by initializing the all ctx kobjects
    belonging to each queue.
    
    Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=908794
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
    06a41a99
blk-mq-sysfs.c 10.6 KB