On Mon, Jan 13, 2014 at 12:37:01PM -0800, Dan Williams wrote: > On Mon, Jan 13, 2014 at 12:06 PM, Todd E Brandt > <todd.e.brandt@xxxxxxxxxxxxxxx> wrote: > > On Fri, Jan 10, 2014 at 07:13:11PM -0800, Dan Williams wrote: > >> On Fri, Jan 10, 2014 at 6:13 PM, Phillip Susi <psusi@xxxxxxxxxx> wrote: > >> > -----BEGIN PGP SIGNED MESSAGE----- > >> > Hash: SHA512 > >> > > >> > On 01/10/2014 06:11 PM, Brandt, Todd E wrote: > >> >> Yes yours is simpler, but it also opens a potential memory issue > >> >> by passing a static int as the return location for the error value. > >> >> I think it's just safer to tell the callback to attempt no return > >> >> value at all, and for that you need to expand it into two > >> >> arguments, one for selection, the other for the output address. > >> > > >> > What sort of memory issue? Also isn't there a system NULL page > >> > somewhere that could be used? > >> > > >> > >> I think the static variable is ok. We can be sure that all eh threads > >> are torn down before libata.ko is unloaded. > > > > Actually there's one other reason. In the ata_port_request_pm function it > > checks to see if there's a previous resume operation pending, and if so > > it calls ata_port_wait_eh in order to wait for it to complete before > > issuing the new suspend. If you just use the (int*)async parameter it > > will return immediately and defer to the caller to try again, like is does > > with SAS. But in our case we *don't* try again, so it would result in the > > resume being skipped. There needs to be a new case where the caller wants > > the call to be asynchronous, and it wants ata_port_request_pm to do its > > own waiting, but doesn't care about the return value. Thus the additional > > parameter. > > I think that is specifically for the libata case of a suspend request > arriving while an async resume is still in flight. Given libata Accoring to the comments it's for a previous resume, not a previous suspend. /* Previous resume operation might still be in * progress. Wait for PM_PENDING to clear. */ if (ap->pflags & ATA_PFLAG_PM_PENDING) { if (async) { *async = -EAGAIN; return 0; } ata_port_wait_eh(ap); WARN_ON(ap->pflags & ATA_PFLAG_PM_PENDING); } I'm going to assume that it was added for a reason, so I've structured my patch in such a way that it doesn't alter the existing logic. Removing that particular check would be a completely different discussion and is out of the scope of this patch. > suspends are synchronous I do not think we have the reverse problem of > resume requests arriving while a suspend is in flight. However, it > might be worth a WARN_ON_ONCE() to document that assumption. > > In the libsas case suspends are asynchronous, but they are flushed by > libsas before any resumes are processed, so there should not be > conflicts. -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html