x86: kmap_atomic() debugging

[ mingo@elte.hu: cleanups and made dependent on CONFIG_DEBUG_HIGHMEM.

  this caught a handful of bugs already, so lets apply it. If it gets
  things wrong we'll disable it. ]

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 46 insertions, 1 deletions

diff --git a/arch/x86/mm/highmem_32.c b/arch/x86/mm/highmem_32.c
index 1c3bf95f7356..3d936f232704 100644
--- a/arch/x86/mm/highmem_32.c
+++ b/arch/x86/mm/highmem_32.c
@@ -18,6 +18,49 @@ void kunmap(struct page *page)
         kunmap_high(page);
 }
 
+static void debug_kmap_atomic_prot(enum km_type type)
+{
+#ifdef CONFIG_DEBUG_HIGHMEM
+        static unsigned warn_count = 10;
+
+        if (unlikely(warn_count == 0))
+                return;
+
+        if (unlikely(in_interrupt())) {
+                if (in_irq()) {
+                        if (type != KM_IRQ0 && type != KM_IRQ1 &&
+                            type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
+                            type != KM_BOUNCE_READ) {
+                                WARN_ON(1);
+                                warn_count--;
+                        }
+                } else if (!irqs_disabled()) {  /* softirq */
+                        if (type != KM_IRQ0 && type != KM_IRQ1 &&
+                            type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
+                            type != KM_SKB_SUNRPC_DATA &&
+                            type != KM_SKB_DATA_SOFTIRQ &&
+                            type != KM_BOUNCE_READ) {
+                                WARN_ON(1);
+                                warn_count--;
+                        }
+                }
+        }
+
+        if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ ||
+                        type == KM_BIO_SRC_IRQ || type == KM_BIO_DST_IRQ) {
+                if (!irqs_disabled()) {
+                        WARN_ON(1);
+                        warn_count--;
+                }
+        } else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
+                if (irq_count() == 0 && !irqs_disabled()) {
+                        WARN_ON(1);
+                        warn_count--;
+                }
+        }
+#endif
+}
+
 /*
  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
  * no global lock is needed and because the kmap code must perform a global TLB
@@ -30,8 +73,10 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
 {
         enum fixed_addresses idx;
         unsigned long vaddr;
-
         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
+
+        debug_kmap_atomic_prot(type);
+
         pagefault_disable();
 
         if (!PageHighMem(page))