On Thu, 6 June 2013 00:16:45 +0800, vaughan wrote: > 于 2013年06月05日 21:27, Jörn Engel 写道: > >On Wed, 5 June 2013 17:18:33 +0800, vaughan wrote: > >> > >>Check and set sdp->exclude should be atomic when set in sg_open(). > > > >The patch is line-wrapped. More importantly, it doesn't seem to do > It's shorter than the original line, so I just leave it like this... Sure. What I meant by line-wrapped is that your mailer mangled the patch. Those two lines should have been one: > >>- ((!sfds_list_empty(sdp) || get_exclude(sdp)) > >>? 0 : set_exclude(sdp, 1))); > >what your description indicates it should do. And lastly, does this > >fix a bug, possibly even one you have a testcase for, or was it found > >by code inspection? > I found it by code inspection. A race condition may happen with the > old code if two threads are both trying to open the same sg with > O_EXCL simultaneously. It's possible that they both find fsds list > is empty and get_exclude(sdp) returns 0, then they both call > set_exclude() and break out from wait_event_interruptible and resume > open. So it's necessary to check again with sg_open_exclusive_lock > held to ensure only one can set sdp->exclude and return >0 to break > out from wait_event loop. Makes sense. And reading the code again, I have to wonder what monkey came up with the get_exclude/set_exclude functions. Can I sucker you into a slightly larger cleanup? I think the entire "get_exclude(sdp)) ? 0 : set_exclude(sdp, 1)" should be simplified. And once you add the try_set_exclude(), set_exclude will only ever do clear_exclude, so you might as well rename and simplify that as well. Let no good deed go unpunished. Jörn -- It's just what we asked for, but not what we want! -- anonymous -- 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
