On 5/22/18 8:29 AM, Vitaly Mayatskih wrote: > Hi, > > I'm working on a new network block device and see occasional deadlocks > when trying to submit_bio from softirq (network rcv handler). This may > be a new use case for blk-mq, but I think context spinlock should be > really taken with bh disabled. I *seem* can avoid the deadlock if bio > has BIO_NOMERGE set, but I need to merge bios for better network > utilization (no merge costs about 15% of bandwidth). Did I miss > something, or the lock indeed needs no bh for that case (recursive > ctx->lock in softirq)?
You can't call submit_bio() from irq/soft irq context, it will potentially sleep for a new request. The various locks for blk-mq have been carefully designed _not_ to need irq/bh disabling, but that's really orthogonal to the previous comment which is your main issue. -- Jens Axboe
