From: hch@infradead.org (Christoph Hellwig)
Subject: [PATCH v2] nvmet: protect sqhd update by a lock
Date: Mon, 16 Oct 2017 23:43:06 -0700 [thread overview]
Message-ID: <20171017064306.GA16133@infradead.org> (raw)
In-Reply-To: <20171016151820.14766-1-jsmart2021@gmail.com>
> if (status)
> nvmet_set_status(req, status);
>
> + spin_lock_irqsave(&req->sq->sqhd_lock, flags);
> if (req->sq->size)
> req->sq->sqhd = (req->sq->sqhd + 1) % req->sq->size;
> req->rsp->sq_head = cpu_to_le16(req->sq->sqhd);
> + spin_unlock_irqrestore(&req->sq->sqhd_lock, flags);
What performance impact does this have? I'm really reluctant to put
an irq disabling spinlock into a hot path for a feature that
theoretically is in the spec but ignored by every host.
I'd much rather play games with cmpxchg or similar here.
next prev parent reply other threads:[~2017-10-17 6:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-16 15:18 [PATCH v2] nvmet: protect sqhd update by a lock James Smart
2017-10-16 15:31 ` Johannes Thumshirn
2017-10-17 6:43 ` Christoph Hellwig [this message]
2017-10-17 14:19 ` James Smart
2017-10-18 7:23 ` Christoph Hellwig
2017-10-18 16:45 ` James Smart
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