cvs commit: src/sys/alpha/alpha busdma_machdep.csrc/sys/i386/i386 src/sys/powerpc/powerpc busdma_machdep.c

[Scott Long]

Nate Lawson wrote:
> On Fri, 27 Jun 2003, Scott Long wrote:
> 
>>  Do the first and mostly mechanical step of adding mutex support to the
>>  bus_dma async callback scheme.  Note that sparc64 does not seem to do
>>  async callbacks.  Note that ia64 callbacks might not be MPSAFE at the
>>  moment.  Note that powerpc doesn't seem to do async callbacks due to
>>  the implementation being incomplete.
>>
>>  Reviewed by:    mostly silence on arch@
>>
>>  Revision  Changes    Path
>>  1.39      +5 -0      src/sys/alpha/alpha/busdma_machdep.c
>>  1.47      +5 -0      src/sys/i386/i386/busdma_machdep.c
>>  1.25      +5 -0      src/sys/ia64/ia64/busdma_machdep.c
>>  1.16      +1 -0      src/sys/powerpc/powerpc/busdma_machdep.c
>>
>>@@ -931,8 +932,12 @@
>> 	while ((map = STAILQ_FIRST(&bounce_map_callbacklist)) != NULL) {
>> 		STAILQ_REMOVE_HEAD(&bounce_map_callbacklist, links);
>> 		mtx_unlock(&bounce_lock);
>>+		if (map->callback_mtx != NULL)
>>+			mtx_lock(map->callback_mtx);
>> 		bus_dmamap_load(map->dmat, map, map->buf, map->buflen,
>> 				map->callback, map->callback_arg, /*flags*/0);
>>+		if (map->callback_mtx != NULL)
>>+			mtx_unlock(map->callback_mtx);
>> 		mtx_lock(&bounce_lock);
>> 	}
>> 	mtx_unlock(&bounce_lock);
> 
> 
> Good to see you working on this area.  Why would callback_mtx be null?  If
> it is null, is it safe to call the function without the lock held?
> 
> -Nate
> 

Yes, calling with a NULL mutex would be allowed and would behave as
expected.

There has been some late-breaking objection to this work, so we'll see 
where it heads.

Scott