sparc32: destroy_context() and switch_mm() needs to disable interrupts.

Load balancing can be triggered in the critical sections protected by
srmmu_context_spinlock in destroy_context() and switch_mm() and can hang
the cpu waiting for the rq lock of another cpu that in turn has called
switch_mm hangning on srmmu_context_spinlock leading to deadlock.

So, disable interrupt while taking srmmu_context_spinlock in
destroy_context() and switch_mm() so we don't deadlock.

See also commit 77b838fa1ef0 ("[SPARC64]: destroy_context() needs to disable
interrupts.")

Signed-off-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 4 deletions

diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
index be65f035d18a..5cbc96d801ff 100644
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -460,10 +460,12 @@ static void __init sparc_context_init(int numctx)
 void switch_mm(struct mm_struct *old_mm, struct mm_struct *mm,
                struct task_struct *tsk)
 {
+        unsigned long flags;
+
         if (mm->context == NO_CONTEXT) {
-                spin_lock(&srmmu_context_spinlock);
+                spin_lock_irqsave(&srmmu_context_spinlock, flags);
                 alloc_context(old_mm, mm);
-                spin_unlock(&srmmu_context_spinlock);
+                spin_unlock_irqrestore(&srmmu_context_spinlock, flags);
                 srmmu_ctxd_set(&srmmu_context_table[mm->context], mm->pgd);
         }
 
@@ -986,14 +988,15 @@ int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
 
 void destroy_context(struct mm_struct *mm)
 {
+        unsigned long flags;
 
         if (mm->context != NO_CONTEXT) {
                 flush_cache_mm(mm);
                 srmmu_ctxd_set(&srmmu_context_table[mm->context], srmmu_swapper_pg_dir);
                 flush_tlb_mm(mm);
-                spin_lock(&srmmu_context_spinlock);
+                spin_lock_irqsave(&srmmu_context_spinlock, flags);
                 free_context(mm->context);
-                spin_unlock(&srmmu_context_spinlock);
+                spin_unlock_irqrestore(&srmmu_context_spinlock, flags);
                 mm->context = NO_CONTEXT;
         }
 }