git: 1a8bcf30f97e - main - amd64: a simplication to pmap_remove_{all, write}

[Alan Cox]

The branch main has been updated by alc:

URL: https://cgit.FreeBSD.org/src/commit/?id=1a8bcf30f97e6153def2af781db2fe54f5c0d106

commit 1a8bcf30f97e6153def2af781db2fe54f5c0d106
Author:     Alan Cox <alc at FreeBSD.org>
AuthorDate: 2021-06-30 05:59:21 +0000
Commit:     Alan Cox <alc at FreeBSD.org>
CommitDate: 2021-06-30 18:12:25 +0000

    amd64: a simplication to pmap_remove_{all,write}
    
    Eliminate some unnecessary unlocking and relocking when we have to retry
    the operation to avoid deadlock.  (All of the other pmap functions that
    iterate over a PV list already implemented retries without these same
    unlocking and relocking operations.)
    
    Reviewed by:    kib, markj
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D30951
---
 sys/amd64/amd64/pmap.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index a4046cc1f687..ea017b8a61a8 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -6307,8 +6307,8 @@ pmap_remove_all(vm_page_t m)
 	lock = VM_PAGE_TO_PV_LIST_LOCK(m);
 	pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy :
 	    pa_to_pvh(VM_PAGE_TO_PHYS(m));
-retry:
 	rw_wlock(lock);
+retry:
 	while ((pv = TAILQ_FIRST(&pvh->pv_list)) != NULL) {
 		pmap = PV_PMAP(pv);
 		if (!PMAP_TRYLOCK(pmap)) {
@@ -6317,7 +6317,6 @@ retry:
 			PMAP_LOCK(pmap);
 			rw_wlock(lock);
 			if (pvh_gen != pvh->pv_gen) {
-				rw_wunlock(lock);
 				PMAP_UNLOCK(pmap);
 				goto retry;
 			}
@@ -6336,7 +6335,6 @@ retry:
 			PMAP_LOCK(pmap);
 			rw_wlock(lock);
 			if (pvh_gen != pvh->pv_gen || md_gen != m->md.pv_gen) {
-				rw_wunlock(lock);
 				PMAP_UNLOCK(pmap);
 				goto retry;
 			}
@@ -8460,8 +8458,8 @@ pmap_remove_write(vm_page_t m)
 	lock = VM_PAGE_TO_PV_LIST_LOCK(m);
 	pvh = (m->flags & PG_FICTITIOUS) != 0 ? &pv_dummy :
 	    pa_to_pvh(VM_PAGE_TO_PHYS(m));
-retry_pv_loop:
 	rw_wlock(lock);
+retry_pv_loop:
 	TAILQ_FOREACH_SAFE(pv, &pvh->pv_list, pv_next, next_pv) {
 		pmap = PV_PMAP(pv);
 		if (!PMAP_TRYLOCK(pmap)) {
@@ -8471,7 +8469,6 @@ retry_pv_loop:
 			rw_wlock(lock);
 			if (pvh_gen != pvh->pv_gen) {
 				PMAP_UNLOCK(pmap);
-				rw_wunlock(lock);
 				goto retry_pv_loop;
 			}
 		}
@@ -8496,7 +8493,6 @@ retry_pv_loop:
 			if (pvh_gen != pvh->pv_gen ||
 			    md_gen != m->md.pv_gen) {
 				PMAP_UNLOCK(pmap);
-				rw_wunlock(lock);
 				goto retry_pv_loop;
 			}
 		}