Date: Sun, 18 Jun 2017 11:04:25 +0100 From: "N.J. Mann" <njm@njm.me.uk> To: Jia-Ju Bai <baijiaju1990@163.com> Cc: freebsd-drivers@freebsd.org Subject: Re: [Bug 220095][PATCH] dpt_scsi: Fix a possible sleep-under-mutex bug in dpt_init Message-ID: <7D8CD40C6A8CDF922B1E15A8@triton.njm.me.uk> In-Reply-To: <20170618094601.40636-1-baijiaju1990@163.com> References: <20170618094601.40636-1-baijiaju1990@163.com>
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Hi,
On Sunday, June 18, 2017 17:46:01 +0800 Jia-Ju Bai <baijiaju1990@163.com> wrote:
> The driver may sleep under a mutex, and the function call path is:
> dpt_init [acquire the mutex]
> dptallocsgmap
> bus_dmamap_load(BUS_DMA_WAITOK) --> may sleep
>
> The possible fix of this bug is to set the last parameter in
> bus_dmamap_load to "BUS_DMA_NOWAIT".
Have you read the manual page for bus_dmamap_load() ?
bus_dmamap_load(dmat, map, buf, buflen, *callback, callback_arg, flags)
Creates a mapping in device visible address space of buflen bytes
of buf, associated with the DMA map map. This call will always
return immediately and will not block for any reason.
I am not saying that your change should not be made, just that your analysis
may be wrong.
Cheers,
Nick.
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