Date: Thu, 12 Jun 2014 11:46:52 -0500 From: Alan Cox <alc@rice.edu> To: John-Mark Gurney <jmg@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r267408 - head/sys/arm/arm Message-ID: <5399D97C.5090608@rice.edu> In-Reply-To: <201406121631.s5CGVFm4033297@svn.freebsd.org> References: <201406121631.s5CGVFm4033297@svn.freebsd.org>
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On 06/12/2014 11:31, John-Mark Gurney wrote: > Author: jmg > Date: Thu Jun 12 16:31:15 2014 > New Revision: 267408 > URL: http://svnweb.freebsd.org/changeset/base/267408 > > Log: > clear the write bit... This allows my AVILA board to survive a > portsnap extract, where previously it would panic.. clearly someone > who knows pmap should optimize this code per alc's comment... > > Submitted by: alc > MFC after: probably Yes, 10.x definitely needs this change. I'm less certain about 9.x, but it's not going to break anything if you do commit it to 9.x. > Modified: > head/sys/arm/arm/pmap.c > > Modified: head/sys/arm/arm/pmap.c > ============================================================================== > --- head/sys/arm/arm/pmap.c Thu Jun 12 16:26:26 2014 (r267407) > +++ head/sys/arm/arm/pmap.c Thu Jun 12 16:31:15 2014 (r267408) > @@ -3034,7 +3034,14 @@ pmap_remove_all(vm_page_t m) > if (TAILQ_EMPTY(&m->md.pv_list)) > return; > rw_wlock(&pvh_global_lock); > - pmap_remove_write(m); > + > + /* > + * XXX This call shouldn't exist. Iterating over the PV list twice, > + * once in pmap_clearbit() and again below, is both unnecessary and > + * inefficient. The below code should itself write back the cache > + * entry before it destroys the mapping. > + */ > + pmap_clearbit(m, PVF_WRITE); > curpm = vmspace_pmap(curproc->p_vmspace); > while ((pv = TAILQ_FIRST(&m->md.pv_list)) != NULL) { > if (flush == FALSE && (pv->pv_pmap == curpm || > @@ -3043,7 +3050,7 @@ pmap_remove_all(vm_page_t m) > > PMAP_LOCK(pv->pv_pmap); > /* > - * Cached contents were written-back in pmap_remove_write(), > + * Cached contents were written-back in pmap_clearbit(), > * but we still have to invalidate the cache entry to make > * sure stale data are not retrieved when another page will be > * mapped under this virtual address. > >
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