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When ring buf full, hw queue will be stopped. While blkif interrupt consume
request and make free space in ring buf, hw queue will be started again.
But since start queue is protected by spin lock while stop not, that will
cause a race.
interrupt: process:
blkif_interrupt() blkif_queue_rq()
kick_pending_request_queues_locked()
blk_mq_start_stopped_hw_queues()
clear_bit(BLK_MQ_S_STOPPED, &hctx->state)
blk_mq_stop_hw_queue(hctx)
blk_mq_run_hw_queue(hctx, async)
If ring buf is made empty in this case, interrupt will never come, then the
hw queue will be stopped forever, all processes waiting for the pending io
in the queue will hung.
Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Ankur Arora <ankur.a.arora@oracle.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.