On Tue, Sep 09, 2014 at 01:14:50PM -0700, Hugh Dickins wrote: > On Mon, 8 Sep 2014, Peter Zijlstra wrote: > > > switch_mm(oldmm, mm, next); > > > + wake_ksm = ksm_switch(mm); > > > > Is this the right mm? > > It's next->mm, that's the one I intended (though the patch might > be equally workable using prev->mm instead: given free rein, I'd > have opted for hooking into both prev and next, but free rein is > definitely not what should be granted around here!). > > > We've just switched the stack, > > I thought that came in switch_to() a few lines further down, > but don't think it matters for this. Ah, yes. Got my task and mm separation messed up. > > so we're looing at next->mm when we switched away from current. > > That might not exist anymore. > > I fail to see how that can be. Looking at the x86 switch_mm(), > I can see it referencing (unsurprisingly!) both old and new mms > at this point, and no reference to an mm is dropped before the > ksm_switch(). oldmm (there called mm) is mmdropped later in > finish_task_switch(). Well, see the above confusion about switch_mm vs switch_to :-/ So if this were switch_to(), we'd see next->mm as before the last context switch. And since that switch fully happened, it would also already have done the finish_task_switch() -> mmdrop().
Attachment:
pgpBOQnW4t6v1.pgp
Description: PGP signature
