9os

commit 52172af3ceef434ab693cadcb3a5dd0a538ec441
parent 2f3d4c8b6a3a403f13f2939e3e1747b02f908e5c
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date:   Thu, 15 Oct 2020 22:24:01 +0200

os9: Improve comments in vmap()

Change-Id: I96c09be6630e20e98103b6fa21b1c55587e64462

Diffstat:
M
src/os9/arch/arm64/mmu.c
 | 
7
+++++--

1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/src/os9/arch/arm64/mmu.c b/src/os9/arch/arm64/mmu.c
@@ -185,8 +185,11 @@ vmap(phyaddr_t pa, uintptr_t va, int perm)
 	/*
 	 * locking is needed if we are in a system
 	 * with SMMUv3 and page tables are shared.
-	 * TODO: use spinlocks here
-	 * TODO: Add information about destroy before make
+	 *
+	 * Here is needed to do a break-before-make as
+	 * the architecture specifies. The first invalidation is
+	 * needed to avoid race conditions in multi processor
+	 * systems.
 	 */
 	lock(&m);
 	*p = INVALID;