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From: Takashi Iwai <tiwai@suse.de>
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Date: Wed, 10 Dec 2014 16:38:30 +0100
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Subject: [PATCH] blk-mq: Fix uninitialized kobject at CPU hotplugging
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When a CPU is hotplugged, the current blk-mq spews a warning like:
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kobject '(null)' (ffffe8ffffc8b5d8): tried to add an uninitialized object, something is seriously wrong.
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CPU: 1 PID: 1386 Comm: systemd-udevd Not tainted 3.18.0-rc7-2.g088d59b-default #1
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Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_171129-lamiak 04/01/2014
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0000000000000000 0000000000000002 ffffffff81605f07 ffffe8ffffc8b5d8
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ffffffff8132c7a0 ffff88023341d370 0000000000000020 ffff8800bb05bd58
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ffff8800bb05bd08 000000000000a0a0 000000003f441940 0000000000000007
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Call Trace:
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[<ffffffff81005306>] dump_trace+0x86/0x330
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[<ffffffff81005644>] show_stack_log_lvl+0x94/0x170
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[<ffffffff81006d21>] show_stack+0x21/0x50
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[<ffffffff81605f07>] dump_stack+0x41/0x51
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[<ffffffff8132c7a0>] kobject_add+0xa0/0xb0
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[<ffffffff8130aee1>] blk_mq_register_hctx+0x91/0xb0
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[<ffffffff8130b82e>] blk_mq_sysfs_register+0x3e/0x60
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[<ffffffff81309298>] blk_mq_queue_reinit_notify+0xf8/0x190
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[<ffffffff8107cfdc>] notifier_call_chain+0x4c/0x70
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[<ffffffff8105fd23>] cpu_notify+0x23/0x50
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[<ffffffff81060037>] _cpu_up+0x157/0x170
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[<ffffffff810600d9>] cpu_up+0x89/0xb0
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[<ffffffff815fa5b5>] cpu_subsys_online+0x35/0x80
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[<ffffffff814323cd>] device_online+0x5d/0xa0
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[<ffffffff81432485>] online_store+0x75/0x80
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[<ffffffff81236a5a>] kernfs_fop_write+0xda/0x150
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[<ffffffff811c5532>] vfs_write+0xb2/0x1f0
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[<ffffffff811c5f42>] SyS_write+0x42/0xb0
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[<ffffffff8160c4ed>] system_call_fastpath+0x16/0x1b
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[<00007f0132fb24e0>] 0x7f0132fb24e0
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This is indeed because of an uninitialized kobject for blk_mq_ctx.
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The blk_mq_ctx kobjects are initialized in blk_mq_sysfs_init(), but it
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goes loop over hctx_for_each_ctx(), i.e. it initializes only for
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online CPUs. Thus, when a CPU is hotplugged, the ctx for the newly
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onlined CPU is registered without initialization.
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This patch fixes the issue by initializing the all ctx kobjects
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belonging to each queue.
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Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=908794
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Cc: <stable@vger.kernel.org>
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Signed-off-by: Takashi Iwai <tiwai@suse.de>
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Signed-off-by: Jens Axboe <axboe@fb.com>
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---
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block/blk-mq-sysfs.c | 9 ++++-----
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1 file changed, 4 insertions(+), 5 deletions(-)
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diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
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index ed5217867555..e0fb3f4a628f 100644
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--- a/block/blk-mq-sysfs.c
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+++ b/block/blk-mq-sysfs.c
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@@ -390,16 +390,15 @@ static void blk_mq_sysfs_init(struct request_queue *q)
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{
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struct blk_mq_hw_ctx *hctx;
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struct blk_mq_ctx *ctx;
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- int i, j;
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+ int i;
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kobject_init(&q->mq_kobj, &blk_mq_ktype);
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- queue_for_each_hw_ctx(q, hctx, i) {
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+ queue_for_each_hw_ctx(q, hctx, i)
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kobject_init(&hctx->kobj, &blk_mq_hw_ktype);
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- hctx_for_each_ctx(hctx, ctx, j)
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- kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
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- }
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+ queue_for_each_ctx(q, ctx, i)
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+ kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
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}
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int blk_mq_register_disk(struct gendisk *disk)
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--
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2.1.0
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