sh: Fix up UP deadlock with SMP-aware cache ops.

This builds on top of the previous reversion and implements a special
on_each_cpu() variant that simple disables preemption across the call
while leaving the interrupt state to the function itself. There were some
unintended consequences with IRQ disabling in some of these paths on UP
that ran in to a deadlock scenario with IRQs being missed.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/mm/cache.c

@@ -34,6 +34,15 @@ static inline void noop__flush_region(void *start, int size)
 {
 }
 
+static inline void cacheop_on_each_cpu(void (*func) (void *info), void *info,
+                                   int wait)
+{
+	preempt_disable();
+	smp_call_function(func, info, wait);
+	func(info);
+	preempt_enable();
+}
+
 void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
 		       unsigned long vaddr, void *dst, const void *src,
 		       unsigned long len)
@@ -149,17 +158,17 @@ void __flush_anon_page(struct page *page, unsigned long vmaddr)
 
 void flush_cache_all(void)
 {
-	on_each_cpu(local_flush_cache_all, NULL, 1);
+	cacheop_on_each_cpu(local_flush_cache_all, NULL, 1);
 }
 
 void flush_cache_mm(struct mm_struct *mm)
 {
-	on_each_cpu(local_flush_cache_mm, mm, 1);
+	cacheop_on_each_cpu(local_flush_cache_mm, mm, 1);
 }
 
 void flush_cache_dup_mm(struct mm_struct *mm)
 {
-	on_each_cpu(local_flush_cache_dup_mm, mm, 1);
+	cacheop_on_each_cpu(local_flush_cache_dup_mm, mm, 1);
 }
 
 void flush_cache_page(struct vm_area_struct *vma, unsigned long addr,
@@ -171,7 +180,7 @@ void flush_cache_page(struct vm_area_struct *vma, unsigned long addr,
 	data.addr1 = addr;
 	data.addr2 = pfn;
 
-	on_each_cpu(local_flush_cache_page, (void *)&data, 1);
+	cacheop_on_each_cpu(local_flush_cache_page, (void *)&data, 1);
 }
 
 void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
@@ -183,12 +192,12 @@ void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
 	data.addr1 = start;
 	data.addr2 = end;
 
-	on_each_cpu(local_flush_cache_range, (void *)&data, 1);
+	cacheop_on_each_cpu(local_flush_cache_range, (void *)&data, 1);
 }
 
 void flush_dcache_page(struct page *page)
 {
-	on_each_cpu(local_flush_dcache_page, page, 1);
+	cacheop_on_each_cpu(local_flush_dcache_page, page, 1);
 }
 
 void flush_icache_range(unsigned long start, unsigned long end)
@@ -199,18 +208,18 @@ void flush_icache_range(unsigned long start, unsigned long end)
 	data.addr1 = start;
 	data.addr2 = end;
 
-	on_each_cpu(local_flush_icache_range, (void *)&data, 1);
+	cacheop_on_each_cpu(local_flush_icache_range, (void *)&data, 1);
 }
 
 void flush_icache_page(struct vm_area_struct *vma, struct page *page)
 {
 	/* Nothing uses the VMA, so just pass the struct page along */
-	on_each_cpu(local_flush_icache_page, page, 1);
+	cacheop_on_each_cpu(local_flush_icache_page, page, 1);
 }
 
 void flush_cache_sigtramp(unsigned long address)
 {
-	on_each_cpu(local_flush_cache_sigtramp, (void *)address, 1);
+	cacheop_on_each_cpu(local_flush_cache_sigtramp, (void *)address, 1);
 }
 
 static void compute_alias(struct cache_info *c)