IMHO cpu_vm_mask should simply and only tell on which CPU a certain
mm_struct is running on. It should tell on which CPUs current->active_mm
is equal to the mm where we reading mm->cpu_vm_mask.
This seems to me a sane semantic and it's easy to enforce it by touching
the cpu-mask bit only while switching_mm in the scheduler code.
The only detail to care about is to flush in memory the cpu_vm_mask
changes before switching pgd and first writing the page-table
changes and then reading the cpu_vm_mask. If some MM will switch CPU while
we are doing the flush that's not a problem because while changing %%cr3
such CPU will automatically flush the TLB.
Currently I believe I am missing something... anyway the below patch seems
to be fine here on 2-way SMP while running msync and swapouts in loop.
diff -urN 2.3.18/arch/i386/kernel/irq.c 2.3.18-smpflush2/arch/i386/kernel/irq.c
--- 2.3.18/arch/i386/kernel/irq.c Wed Sep 8 00:25:40 1999
+++ 2.3.18-smpflush2/arch/i386/kernel/irq.c Sat Sep 11 15:35:51 1999
@@ -151,10 +151,7 @@
static inline void check_smp_invalidate(int cpu)
{
if (test_bit(cpu, &smp_invalidate_needed)) {
- struct mm_struct *mm = current->mm;
clear_bit(cpu, &smp_invalidate_needed);
- if (mm)
- atomic_set_mask(1 << cpu, &mm->cpu_vm_mask);
local_flush_tlb();
}
}
diff -urN 2.3.18/arch/i386/kernel/smp.c 2.3.18-smpflush2/arch/i386/kernel/smp.c
--- 2.3.18/arch/i386/kernel/smp.c Wed Sep 8 18:18:45 1999
+++ 2.3.18-smpflush2/arch/i386/kernel/smp.c Sat Sep 11 15:38:22 1999
@@ -1635,10 +1635,7 @@
* Take care of "crossing" invalidates
*/
if (test_bit(cpu, &smp_invalidate_needed)) {
- struct mm_struct *mm = current->mm;
clear_bit(cpu, &smp_invalidate_needed);
- if (mm)
- atomic_set_mask(1 << cpu, &mm->cpu_vm_mask);
local_flush_tlb();
}
--stuck;
@@ -1660,39 +1657,33 @@
*/
void flush_tlb_current_task(void)
{
- unsigned long vm_mask = 1 << current->processor;
- struct mm_struct *mm = current->mm;
- unsigned long cpu_mask = mm->cpu_vm_mask & ~vm_mask;
+ unsigned long cpu_mask;
- mm->cpu_vm_mask = vm_mask;
+ mb();
+ cpu_mask = current->mm->cpu_vm_mask & ~(1 << smp_processor_id());
flush_tlb_others(cpu_mask);
local_flush_tlb();
}
void flush_tlb_mm(struct mm_struct * mm)
{
- unsigned long vm_mask = 1 << current->processor;
- unsigned long cpu_mask = mm->cpu_vm_mask & ~vm_mask;
+ unsigned long cpu_mask;
- mm->cpu_vm_mask = 0;
- if (current->active_mm == mm) {
- mm->cpu_vm_mask = vm_mask;
+ mb();
+ cpu_mask = mm->cpu_vm_mask & ~(1 << smp_processor_id());
+ if (current->active_mm == mm)
local_flush_tlb();
- }
flush_tlb_others(cpu_mask);
}
void flush_tlb_page(struct vm_area_struct * vma, unsigned long va)
{
- unsigned long vm_mask = 1 << current->processor;
- struct mm_struct *mm = vma->vm_mm;
- unsigned long cpu_mask = mm->cpu_vm_mask & ~vm_mask;
+ unsigned long cpu_mask;
- mm->cpu_vm_mask = 0;
- if (current->active_mm == mm) {
+ mb();
+ cpu_mask = vma->vm_mm->cpu_vm_mask & ~(1 << smp_processor_id());
+ if (current->active_mm == vma->vm_mm)
__flush_tlb_one(va);
- mm->cpu_vm_mask = vm_mask;
- }
flush_tlb_others(cpu_mask);
}
@@ -1934,12 +1925,8 @@
struct task_struct *tsk = current;
unsigned int cpu = tsk->processor;
- if (test_and_clear_bit(cpu, &smp_invalidate_needed)) {
- struct mm_struct *mm = tsk->mm;
- if (mm)
- atomic_set_mask(1 << cpu, &mm->cpu_vm_mask);
+ if (test_and_clear_bit(cpu, &smp_invalidate_needed))
local_flush_tlb();
- }
ack_APIC_irq();
}
diff -urN 2.3.18/include/asm-i386/mmu_context.h 2.3.18-smpflush2/include/asm-i386/mmu_context.h
--- 2.3.18/include/asm-i386/mmu_context.h Fri Sep 10 22:11:40 1999
+++ 2.3.18-smpflush2/include/asm-i386/mmu_context.h Sat Sep 11 15:41:06 1999
@@ -12,7 +12,6 @@
static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk, unsigned cpu)
{
-
if (prev != next) {
/*
* Re-load LDT if necessary
@@ -20,11 +19,13 @@
if (prev->segments != next->segments)
load_LDT(next);
+ clear_bit(cpu, &prev->cpu_vm_mask);
+ set_bit(cpu, &next->cpu_vm_mask);
+ /* on i386 set_bit also reoder memory accesses on the CPU */
+
/* Re-load page tables */
asm volatile("movl %0,%%cr3": :"r" (__pa(next->pgd)));
- clear_bit(cpu, &prev->cpu_vm_mask);
}
- set_bit(cpu, &next->cpu_vm_mask);
}
#define activate_mm(prev, next) \
Andrea
-
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