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GET /api/patches/794468/?format=api
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{
    "id": 794468,
    "url": "http://patchwork.ozlabs.org/api/patches/794468/?format=api",
    "web_url": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/1501166846.2516.1.camel@wdc.com/",
    "project": {
        "id": 2,
        "url": "http://patchwork.ozlabs.org/api/projects/2/?format=api",
        "name": "Linux PPC development",
        "link_name": "linuxppc-dev",
        "list_id": "linuxppc-dev.lists.ozlabs.org",
        "list_email": "linuxppc-dev@lists.ozlabs.org",
        "web_url": "https://github.com/linuxppc/wiki/wiki",
        "scm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git",
        "webscm_url": "https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/",
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    "msgid": "<1501166846.2516.1.camel@wdc.com>",
    "list_archive_url": "https://lore.kernel.org/linuxppc-dev/1501166846.2516.1.camel@wdc.com/",
    "date": "2017-07-27T14:47:28",
    "name": "blk_mq_sched_insert_request: inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage",
    "commit_ref": null,
    "pull_url": null,
    "state": "not-applicable",
    "archived": false,
    "hash": "8e241e2d85c8cc8b3da13132aab04130c8eab717",
    "submitter": {
        "id": 71843,
        "url": "http://patchwork.ozlabs.org/api/people/71843/?format=api",
        "name": "Bart Van Assche",
        "email": "Bart.VanAssche@wdc.com"
    },
    "delegate": null,
    "mbox": "http://patchwork.ozlabs.org/project/linuxppc-dev/patch/1501166846.2516.1.camel@wdc.com/mbox/",
    "series": [],
    "comments": "http://patchwork.ozlabs.org/api/patches/794468/comments/",
    "check": "pending",
    "checks": "http://patchwork.ozlabs.org/api/patches/794468/checks/",
    "tags": {},
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        "From": "Bart Van Assche <Bart.VanAssche@wdc.com>",
        "To": "\"mpe@ellerman.id.au\" <mpe@ellerman.id.au>, \"axboe@kernel.dk\"\n\t<axboe@kernel.dk>",
        "Subject": "Re: blk_mq_sched_insert_request: inconsistent {SOFTIRQ-ON-W} ->\n\t{IN-SOFTIRQ-W} usage",
        "Thread-Topic": "blk_mq_sched_insert_request: inconsistent {SOFTIRQ-ON-W} ->\n\t{IN-SOFTIRQ-W} usage",
        "Thread-Index": "AQHTBpbYyx2cmVtqXUGNBRJ+OE1bb6JntOSAgAAMdAA=",
        "Date": "Thu, 27 Jul 2017 14:47:28 +0000",
        "Message-ID": "<1501166846.2516.1.camel@wdc.com>",
        "References": "<87a83qfosu.fsf@concordia.ellerman.id.au>\n\t<073ed79c-11ce-e86c-a905-91fd28675d47@kernel.dk>",
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    },
    "content": "On Thu, 2017-07-27 at 08:02 -0600, Jens Axboe wrote:\n> The bug looks like SCSI running the queue inline from IRQ\n> context, that's not a good idea. Can you confirm the below works for\n> you?\n> \n> \n> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c\n> index f6097b89d5d3..78740ebf966c 100644\n> --- a/drivers/scsi/scsi_lib.c\n> +++ b/drivers/scsi/scsi_lib.c\n> @@ -497,7 +497,7 @@ static void scsi_run_queue(struct request_queue *q)\n>  \t\tscsi_starved_list_run(sdev->host);\n>  \n>  \tif (q->mq_ops)\n> -\t\tblk_mq_run_hw_queues(q, false);\n> +\t\tblk_mq_run_hw_queues(q, true);\n>  \telse\n>  \t\tblk_run_queue(q);\n>  }\n\nHello Jens,\n\nscsi_run_queue() works fine if no scheduler is configured. Additionally, that\ncode predates the introduction of blk-mq I/O schedulers. I think it is\nnontrivial for block driver authors to figure out that a queue has to be run\nfrom process context if a scheduler has been configured that does not support\nto be run from interrupt context. How about adding WARN_ON_ONCE(in_interrupt())\nto blk_mq_start_hw_queue() or replacing the above patch by the following:\n\n\nSubject: [PATCH] blk-mq: Make it safe to call blk_mq_start_hw_queues() from interrupt context\n\nblk_mq_start_hw_queues() triggers a queue run. Some functions that\nget called to run a queue, e.g. dd_dispatch_request(), are not IRQ-safe.\nHence run the queue asynchronously if blk_mq_start_hw_queues() is called\nfrom interrupt context.\n\nSigned-off-by: Bart Van Assche <bart.vanassche@wdc.com>\n---\n block/blk-mq.c | 2 +-\n 1 file changed, 1 insertion(+), 1 deletion(-)\n\nThanks,\n\nBart.",
    "diff": "diff --git a/block/blk-mq.c b/block/blk-mq.c\nindex 041f7b7fa0d6..c5cb3b2aabcf 100644\n--- a/block/blk-mq.c\n+++ b/block/blk-mq.c\n@@ -1251,7 +1251,7 @@ void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)\n {\n \tclear_bit(BLK_MQ_S_STOPPED, &hctx->state);\n \n-\tblk_mq_run_hw_queue(hctx, false);\n+\tblk_mq_run_hw_queue(hctx, in_interrupt());\n }\n EXPORT_SYMBOL(blk_mq_start_hw_queue);\n \n",
    "prefixes": []
}