Re: 2.2.10 SMP Spinlock

Anton Blanchard (anton@progsoc.uts.edu.au)
Thu, 5 Aug 1999 21:06:45 +1000

> We are running Linux 2.2.10 on a couple of SS-10's here, both of which
> are equipped with quad Ross RTK-625 Hypersparc CPU's.
>
> One machine is used for news, it has a second disk controller, 256mb of
> memory. So far it has been completely stable.
>
> The other is used for a web server running Apache 1.3.3p3. It has only
> the SCSI controller built into the SS-10 but also has 384mb of RAM. It has not
> been completely stable. It is hanging with a message about spinlock scrolling
> up the screen.

There are some races during context creation and switching on SMP
sparc32. This fixes one problem and if you have contexts > NR_TASKS then
you probably wont see the others. (There are problems when we need to
steal a context from antother cpu)

Anton

--- linux/arch/sparc/mm/srmmu.c Sat Jul 24 14:03:58 1999
+++ linux_work/arch/sparc/mm/srmmu.c Wed Jul 28 19:56:45 1999
@@ -114,6 +114,7 @@
#define srmmu_ahashfn(addr) ((addr) >> 24)

int viking_mxcc_present = 0;
+static spinlock_t srmmu_context_spinlock = SPIN_LOCK_UNLOCKED;

/* Physical memory can be _very_ non-contiguous on the sun4m, especially
* the SS10/20 class machines and with the latest openprom revisions.
@@ -819,7 +820,9 @@
static void srmmu_switch_to_context(struct task_struct *tsk)
{
if(tsk->mm->context == NO_CONTEXT) {
+ spin_lock(&srmmu_context_spinlock);
alloc_context(tsk->mm);
+ spin_unlock(&srmmu_context_spinlock);
ctxd_set(&srmmu_context_table[tsk->mm->context], tsk->mm->pgd);
}
srmmu_set_context(tsk->mm->context);
@@ -827,7 +830,9 @@

static void srmmu_init_new_context(struct mm_struct *mm)
{
+ spin_lock(&srmmu_context_spinlock);
alloc_context(mm);
+ spin_unlock(&srmmu_context_spinlock);

flush_cache_mm(mm);
ctxd_set(&srmmu_context_table[mm->context], mm->pgd);
@@ -1398,7 +1403,9 @@
if(tsk->mm->context == NO_CONTEXT) {
ctxd_t *ctxp;

+ spin_lock(&srmmu_context_spinlock);
alloc_context(tsk->mm);
+ spin_unlock(&srmmu_context_spinlock);
ctxp = &srmmu_context_table[tsk->mm->context];
srmmu_set_entry((pte_t *)ctxp, __pte((SRMMU_ET_PTD | (srmmu_v2p((unsigned long) tsk->mm->pgd) >> 4))));
hypersparc_flush_page_to_ram((unsigned long)ctxp);
@@ -1411,7 +1418,9 @@
{
ctxd_t *ctxp;

+ spin_lock(&srmmu_context_spinlock);
alloc_context(mm);
+ spin_unlock(&srmmu_context_spinlock);

ctxp = &srmmu_context_table[mm->context];
srmmu_set_entry((pte_t *)ctxp, __pte((SRMMU_ET_PTD | (srmmu_v2p((unsigned long) mm->pgd) >> 4))));

-
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