Matthew Wilcox wrote: > On Thu, Mar 25, 2010 at 11:21:17AM -0600, James Bottomley wrote: >> On Thu, 2010-03-25 at 18:05 +0100, Stefan Bader wrote: >>> The following patch was tested and seemed to avoid the warning. Howver >>> I am not completely sure that none of the later functions need to be >>> protected with spinlocks. Though it feels ok. But maybe someone can do >>> some sanity checking. >> So, I'm afraid you're right, the patch as is won't work ... the problem >> is that __sym_mfree_dma does list manipulation and for safety that has >> to be under a lock. >> >> The inception of this problem is that ARM needs a sleeping function on >> DMA free but nothing else does so, on every platform that sym2 is >> supported, this warning is bogus. > > Oh good, I'm glad you wrote this, it saves me the typing ;-) > >> One way of getting rid of it might be to undef SYM_MEM_FREE_UNUSED which >> will prevent the free routines actually from releasing memory ... >> another might be to drop the lock and reacquire it around the free ... >> but that's sitting in a list traversal function so it may expose us to >> list races again, so really the whole of the freeing routines would have >> to be re-written to be list safe under lock ... > > The solution I'd suggest is to take out the WARN_ON in the x86 code. > It's never going to cause trouble on x86. Ok, thanks for the infos. Sounds like this is the quickest solution to a problem which is not a real one for x86. Maybe limit it to just ARM if that's the only architecture that has problems with it. Stefan > The real solution is to use DMA pools, but my supply of tuits is quite > limited these days, and converting sym2 to modern APIs isn't high on > my priority list. > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
