[Bug 220032] [if_alc] sys/dev/alc/if_alc.c: sleep-under-mutex bugs

[Jia-Ju Bai]

Hi,

I have read the manual page ofbus_dmamap_load and other dmamap-load 
related functions.
These calls will always return immediately and will not block for any 
reason.
Sorry for my wrong report, please ignore it.

Thanks,
Jia-Ju Bai

On 2017/6/18 15:47, Jia-Ju Bai wrote:
> Thanks a lot, your advice is very helpful :)
> I will submit a patch according to your advice, and update my bug report.
>
> By the way, I have found many similar possible bugs in network drivers 
> in FreeBSD.
> And they are all caused by "BUS_DMA_WAITOK" in bus_dmamap_load and 
> other dmamap-load related functions.
> If my reported bugs can be quickly confirmed, I will write and submit 
> patches for them as soon as possible.
> I am looking forward to helpful comments and advice :)
>
> Thanks,
> Jia-Ju Bai
>
> On 2017/6/18 13:31, Kevin Oberman wrote:
>> On Fri, Jun 16, 2017 at 2:03 AM, Jia-Ju Bai <baijiaju1990 at 163.com 
>> <mailto:baijiaju1990 at 163.com>> wrote:
>>
>>     The alc driver may sleep under a mutex, and the function call
>>     paths in file
>>     "sys/dev/alc/if_alc.c" in FreeBSD 11.0 is:
>>     alc_resume [line 2648: acquire the mutex]
>>       alc_init_locked [line 2664]
>>         alc_init_rx_ring [line 3911]
>>           alc_newbuf [line 4469]
>>             bus_dmamap_load_mbuf_sg(BUS_DMA_WAITOK) [line 3472] -->
>>     may sleep
>>
>>     alc_int_task [line 3330: acquire the mutex]
>>       alc_start_locked [line 3372]
>>         alc_encap [line 2942]
>>           bus_dmamap_load_mbuf_sg(BUS_DMA_WAITOK) [line 2780] --> may
>>     sleep
>>
>>     The possible fix of these bugs is to set the last parameter in
>>     bus_dmamap_load_mbuf_sg to "BUS_DMA_NOWAIT".
>>
>>     This bug is found by a static analysis tool written by myself,
>>     and it is
>>     checked by my review of the FreeBSD code.
>>
>>     By the way, I am a freshman in developing FreeBSD drivers, and I
>>     am willing to
>>     submit a patch. But I do not know how to write and submit a
>>     patch, and where to
>>     submit, so I am looking forward to useful advice :)
>>
>>     Jia-Ju Bai
>>
>>
>> To submit a patch, use svn to download the source from a repository. 
>> Be sure the file in your source directory is the current, unmodified 
>> file.
>> Edit the file or files as needed to correct the bug
>> Generate the diff with the command "svn diff 
>> path-to-directory-containing-file(s) > diff-file.diff"
>> Update the bug report attaching the patch (with a brief description)
>> --
>> Kevin Oberman, Part time kid herder and retired Network Engineer
>> E-mail: rkoberman at gmail.com <mailto:rkoberman at gmail.com>
>> PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683
>