From: Tomas Hruby <tom@minix3.org>
Date: Wed, 15 Sep 2010 14:10:36 +0000 (+0000)
Subject: SMP - Free PDE slots are split among CPU
X-Git-Tag: v3.2.0~853
X-Git-Url: http://zhaoyanbai.com/repos/%22../static/howto.html?a=commitdiff_plain;h=93b9873a562b11dfedf5f4e53ef87bf256d80207;p=minix.git

SMP - Free PDE slots are split among CPU

- cross-address space copies use these slots to map user memory for
  kernel. This avoid any collisions between CPUs

- well, we only have a single CPU running at a time, this is just to
  be safe for the future
---

diff --git a/kernel/arch/i386/memory.c b/kernel/arch/i386/memory.c
index 35fa5f687..e1307df69 100644
--- a/kernel/arch/i386/memory.c
+++ b/kernel/arch/i386/memory.c
@@ -31,7 +31,8 @@ PUBLIC int i386_paging_enabled = 0;
 
 PRIVATE int psok = 0;
 
-#define MAX_FREEPDES (3 * CONFIG_MAX_CPUS)
+#define FREE_PDES_PER_CPU	3
+#define MAX_FREEPDES		(FREE_PDES_PER_CPU * CONFIG_MAX_CPUS)
 PRIVATE int nfreepdes = 0, freepdes[MAX_FREEPDES];
 
 #define HASPT(procptr) ((procptr)->p_seg.p_cr3 != 0)
@@ -79,7 +80,12 @@ PRIVATE phys_bytes createpde(
 	phys_bytes offset;
 	int pde;
 
-	assert(free_pde_idx >= 0 && free_pde_idx < nfreepdes);
+	assert(free_pde_idx >= 0 && free_pde_idx < FREE_PDES_PER_CPU);
+
+	/* make the index CPU local */
+	free_pde_idx += cpuid * FREE_PDES_PER_CPU;
+	assert(free_pde_idx < nfreepdes);
+
 	pde = freepdes[free_pde_idx];
 	assert(pde >= 0 && pde < 1024);