git: 94e5ec7f869e - stable/14 - vm_page: Use atomic loads for cmpset loops

The branch stable/14 has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=94e5ec7f869e244afa174af2f8a61e4355a2cb73

commit 94e5ec7f869e244afa174af2f8a61e4355a2cb73
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2024-10-07 20:50:36 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2024-10-15 12:39:44 +0000

    vm_page: Use atomic loads for cmpset loops
    
    Make sure that the compiler loads the initial value value only once.
    Because atomic_fcmpset is used to load the value for subsequent
    iterations, this is probably not needed, but we should not rely on that.
    
    I verified that code generated for an amd64 GENERIC kernel does not
    change.
    
    Reviewed by:    dougm, alc, kib
    Tested by:      pho
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D46943
    
    (cherry picked from commit d8b32da2354d2fd72ae017fd63affa3684786e1f)
---
 sys/vm/vm_page.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index fe104e1e87af..7c3083de42de 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -1972,7 +1972,7 @@ _vm_domain_allocate(struct vm_domain *vmd, int req_class, int npages)
 	 * Attempt to reserve the pages.  Fail if we're below the limit.
 	 */
 	limit += npages;
-	old = vmd->vmd_free_count;
+	old = atomic_load_int(&vmd->vmd_free_count);
 	do {
 		if (old < limit)
 			return (0);
@@ -4054,7 +4054,7 @@ vm_page_wire_mapped(vm_page_t m)
 {
 	u_int old;
 
-	old = m->ref_count;
+	old = atomic_load_int(&m->ref_count);
 	do {
 		KASSERT(old > 0,
 		    ("vm_page_wire_mapped: wiring unreferenced page %p", m));
@@ -4088,7 +4088,7 @@ vm_page_unwire_managed(vm_page_t m, uint8_t nqueue, bool noreuse)
 	 * Use a release store when updating the reference count to
 	 * synchronize with vm_page_free_prep().
 	 */
-	old = m->ref_count;
+	old = atomic_load_int(&m->ref_count);
 	do {
 		KASSERT(VPRC_WIRE_COUNT(old) > 0,
 		    ("vm_page_unwire: wire count underflow for page %p", m));
@@ -4383,7 +4383,7 @@ vm_page_try_blocked_op(vm_page_t m, void (*op)(vm_page_t))
 	    ("vm_page_try_blocked_op: page %p is not busy", m));
 	VM_OBJECT_ASSERT_LOCKED(m->object);
 
-	old = m->ref_count;
+	old = atomic_load_int(&m->ref_count);
 	do {
 		KASSERT(old != 0,
 		    ("vm_page_try_blocked_op: page %p has no references", m));