Messages in this thread | | | Date | Tue, 30 Jun 2009 08:09:08 -0400 | From | Gregory Haskins <> | Subject | Re: [PATCH v4] slow-work: add (module*)work->ops->owner to fix races with module clients |
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Michael S. Tsirkin wrote: > On Tue, Jun 30, 2009 at 10:18:32AM +0100, steve@chygwyn.com wrote: > >> Hi, >> >> On Tue, Jun 30, 2009 at 12:07:15PM +0300, Michael S. Tsirkin wrote: >> >>> On Tue, Jun 30, 2009 at 09:43:03AM +0100, Steven Whitehouse wrote: >>> >>>> Hi, >>>> >>>> I'm happy to ACK this, but the race doesn't exist in GFS2's case because >>>> we wait for all work related to each GFS2 fs at umount time and the >>>> module unload cannot happen until all GFS2 fs are umounted, >>>> >>>> Steve. >>>> >>> I wonder whether the following holds: >>> >>> static void gfs2_recover_put_ref(struct slow_work *work) >>> { >>> struct gfs2_jdesc *jd = container_of(work, struct gfs2_jdesc, jd_work); >>> clear_bit(JDF_RECOVERY, &jd->jd_flags); >>> smp_mb__after_clear_bit(); >>> wake_up_bit(&jd->jd_flags, JDF_RECOVERY); >>> >>> <- umount can complete here? >>> >>> } >>> >>> >>> If yes, .text of the module could go away between the point marked by <- >>> and return from gfs2_recover_put_ref. >>> >>> >>> >> Well in theory, yes. In reality I don't think it could ever happen >> > > Right. IIUC, that's all Gregory's patch is trying to address: a > theoretical race condition. > > Yeah, I never actually saw a crash. I just noticed the hole via code inspection.
Regards, -Greg
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