On Wed, Jun 30, 1999 at 03:39:26PM +0200, Einar Floystad Dorum wrote:
> On my SX164 running RH 6.0 (glibc 2.1, egcs 1.1.2) any program using
> pthread will segfault or do an invalid instruction after a short
> time. This happens on both 2.2.10 and 2.2.11-pre1 + Richard
> Henderson's d-2211-rth1.gz. The enclosed pthread test program will
> always segfault inside one of the pthread_* calls.
Indeed.
Somehow, while guessing how things might could be optimized, I forgot
that flush_tlb_mm allocates new ASNs. So all the hemming and hawing
about tss.mm_context was garbage. We have to copy the mm->context
into tss.asn every time we're scheduled. Without fail.
Here's a patch against 2.2.11-rth1.
Thanks for the wonderful test case.
r~
--BOKacYhQ+x31HxR3
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment; filename=d-2211-rth2
diff -rup 2.2.11-rth1/Makefile 2.2.11-axp/Makefile
--- 2.2.11-rth1/Makefile Sun Jul 4 22:46:49 1999
+++ 2.2.11-axp/Makefile Sun Jul 4 22:54:10 1999
@@ -1,7 +1,7 @@
VERSION = 2
PATCHLEVEL = 2
SUBLEVEL = 11
-EXTRAVERSION = -rth1
+EXTRAVERSION = -rth2
ARCH := $(shell uname -m | sed -e s/i.86/i386/ -e s/sun4u/sparc64/ -e s/arm.*/arm/ -e s/sa110/arm/)
diff -rup 2.2.11-rth1/arch/alpha/kernel/process.c 2.2.11-axp/arch/alpha/kernel/process.c
--- 2.2.11-rth1/arch/alpha/kernel/process.c Sun Jul 4 22:46:49 1999
+++ 2.2.11-axp/arch/alpha/kernel/process.c Sun Jul 4 22:37:30 1999
@@ -329,7 +329,6 @@ int copy_thread(int nr, unsigned long cl
p->tss.ksp = (unsigned long) childstack;
p->tss.pal_flags = 1; /* set FEN, clear everything else */
p->tss.flags = current->tss.flags;
- p->tss.mm_context = p->tss.asn = 0;
return 0;
}
diff -rup 2.2.11-rth1/arch/alpha/kernel/smp.c 2.2.11-axp/arch/alpha/kernel/smp.c
--- 2.2.11-rth1/arch/alpha/kernel/smp.c Sun Jul 4 22:46:49 1999
+++ 2.2.11-axp/arch/alpha/kernel/smp.c Sun Jul 4 22:30:13 1999
@@ -864,9 +864,11 @@ ipi_flush_tlb_mm(void *x)
void
flush_tlb_mm(struct mm_struct *mm)
{
- if (mm == current->mm)
+ if (mm == current->mm) {
flush_tlb_current(mm);
- else
+ if (atomic_read(&mm->count) == 1)
+ return;
+ } else
flush_tlb_other(mm);
if (smp_call_function(ipi_flush_tlb_mm, mm, 1, 1)) {
@@ -894,15 +896,17 @@ flush_tlb_page(struct vm_area_struct *vm
struct flush_tlb_page_struct data;
struct mm_struct *mm = vma->vm_mm;
+ if (mm == current->mm) {
+ flush_tlb_current_page(mm, vma, addr);
+ if (atomic_read(¤t->mm->count) == 1)
+ return;
+ } else
+ flush_tlb_other(mm);
+
data.vma = vma;
data.mm = mm;
data.addr = addr;
- if (mm == current->mm)
- flush_tlb_current_page(mm, vma, addr);
- else
- flush_tlb_other(mm);
-
if (smp_call_function(ipi_flush_tlb_page, &data, 1, 1)) {
printk(KERN_CRIT "flush_tlb_page: timed out\n");
}
diff -rup 2.2.11-rth1/arch/alpha/mm/fault.c 2.2.11-axp/arch/alpha/mm/fault.c
--- 2.2.11-rth1/arch/alpha/mm/fault.c Sun Jul 4 22:46:49 1999
+++ 2.2.11-axp/arch/alpha/mm/fault.c Sun Jul 4 22:38:01 1999
@@ -42,7 +42,6 @@ get_new_mmu_context(struct task_struct *
{
unsigned long new = __get_new_mmu_context();
mm->context = new;
- p->tss.mm_context = new;
p->tss.asn = new & HARDWARE_ASN_MASK;
}
diff -rup 2.2.11-rth1/include/asm-alpha/mmu_context.h 2.2.11-axp/include/asm-alpha/mmu_context.h
--- 2.2.11-rth1/include/asm-alpha/mmu_context.h Sun Jul 4 22:46:49 1999
+++ 2.2.11-axp/include/asm-alpha/mmu_context.h Sun Jul 4 22:51:39 1999
@@ -75,9 +75,9 @@ extern unsigned long last_asn;
/*
* NOTE! The way this is set up, the high bits of the "asn_cache" (and
- * "mm->context" and tss.mm_context) are the ASN _version_ code. A version
- * of 0 is always considered invalid, so to invalidate another process you
- * only need to do "p->tss.mm_context = p->mm->context = 0".
+ * "mm->context") are the ASN _version_ code. A version of 0 is always
+ * considered invalid, so to invalidate another process you only need
+ * to do "p->mm->context = 0".
*
* If we need more ASN's than the processor has, we invalidate the old
* user TLB's (tbiap()) and start a new ASN version. That will automatically
@@ -127,19 +127,23 @@ ev5_get_mmu_context(struct task_struct *
{
/* Check if our ASN is of an older version, or on a different CPU,
and thus invalid. */
+ /* ??? If we have two threads on different cpus, we'll continually
+ fight over the context. Find a way to record a per-mm, per-cpu
+ value for the asn. */
unsigned long asn = cpu_last_asn(smp_processor_id());
struct mm_struct *mm = p->mm;
unsigned long mmc = mm->context;
- if ((p->tss.mm_context ^ asn) & ~HARDWARE_ASN_MASK) {
- if ((mmc ^ asn) & ~HARDWARE_ASN_MASK) {
- mmc = __get_new_mmu_context();
- mm->context = mmc;
- }
- p->tss.mm_context = mmc;
- p->tss.asn = mmc & HARDWARE_ASN_MASK;
+ if ((mmc ^ asn) & ~HARDWARE_ASN_MASK) {
+ mmc = __get_new_mmu_context();
+ mm->context = mmc;
}
+
+ /* Always update the PCB ASN. Another thread may have allocated
+ a new mm->context (via flush_tlb_mm) without the ASN serial
+ number wrapping. We have no way to detect when this is needed. */
+ p->tss.asn = mmc & HARDWARE_ASN_MASK;
}
#ifdef CONFIG_ALPHA_GENERIC
diff -rup 2.2.11-rth1/include/asm-alpha/pgtable.h 2.2.11-axp/include/asm-alpha/pgtable.h
--- 2.2.11-rth1/include/asm-alpha/pgtable.h Sat Jun 12 06:40:54 1999
+++ 2.2.11-axp/include/asm-alpha/pgtable.h Sun Jul 4 22:51:39 1999
@@ -49,7 +49,6 @@ ev4_flush_tlb_other(struct mm_struct *mm
__EXTERN_INLINE void
ev5_flush_tlb_current(struct mm_struct *mm)
{
- mm->context = 0;
get_new_mmu_context(current, mm);
reload_context(current);
}
diff -rup 2.2.11-rth1/include/asm-alpha/processor.h 2.2.11-axp/include/asm-alpha/processor.h
--- 2.2.11-rth1/include/asm-alpha/processor.h Sun Jul 4 22:46:49 1999
+++ 2.2.11-axp/include/asm-alpha/processor.h Sun Jul 4 21:58:28 1999
@@ -55,15 +55,6 @@ struct thread_struct {
*/
unsigned long flags;
- /* The full version of the ASN including serial number.
-
- Two threads running on two different processors must of necessity
- have different serial numbers. Having this duplicated from
- mm->context allows them to be slightly out of sync preventing
- the asn from incrementing each and every time the two threads
- are scheduled. */
- unsigned long mm_context;
-
/* Perform syscall argument validation (get/set_fs). */
mm_segment_t fs;
@@ -80,7 +71,7 @@ struct thread_struct {
0, 0, 0, \
0, 0, 0, \
0, 0, 0, \
- 0, 0, \
+ 0, \
KERNEL_DS \
}
--BOKacYhQ+x31HxR3--
-
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