1 files changed, 20 insertions, 24 deletions

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 1fc3192468ef..c49cb6d6b838 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -1026,8 +1026,8 @@ irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
 }
 
 static DEFINE_PER_CPU(unsigned, xed_nesting_count);
-static DEFINE_PER_CPU(unsigned int, last_word_idx) = { BITS_PER_LONG - 1 };
-static DEFINE_PER_CPU(unsigned int, last_bit_idx) = { BITS_PER_LONG - 1 };
+static DEFINE_PER_CPU(unsigned int, current_word_idx);
+static DEFINE_PER_CPU(unsigned int, current_bit_idx);
 
 /*
  * Mask out the i least significant bits of w
@@ -1065,23 +1065,21 @@ static void __xen_evtchn_do_upcall(void)
 #endif
                 pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
 
-                word_idx = __this_cpu_read(last_word_idx);
-                bit_idx = __this_cpu_read(last_bit_idx);
+                word_idx = __this_cpu_read(current_word_idx);
+                bit_idx = __this_cpu_read(current_bit_idx);
 
                 while (pending_words != 0) {
                         unsigned long pending_bits;
                         unsigned long words;
 
-                        word_idx = (word_idx + 1) % BITS_PER_LONG;
                         words = MASK_LSBS(pending_words, word_idx);
 
                         /*
-                         * If we masked out all events, wrap around to the
-                         * beginning.
+                         * If we masked out all events, wrap to beginning.
                          */
                         if (words == 0) {
-                                word_idx = BITS_PER_LONG - 1;
-                                bit_idx = BITS_PER_LONG - 1;
+                                word_idx = 0;
+                                bit_idx = 0;
                                 continue;
                         }
                         word_idx = __ffs(words);
@@ -1093,14 +1091,11 @@ static void __xen_evtchn_do_upcall(void)
 
                                 pending_bits = active_evtchns(cpu, s, word_idx);
 
-                                bit_idx = (bit_idx + 1) % BITS_PER_LONG;
                                 bits = MASK_LSBS(pending_bits, bit_idx);
 
                                 /* If we masked out all events, move on. */
-                                if (bits == 0) {
-                                        bit_idx = BITS_PER_LONG - 1;
+                                if (bits == 0)
                                         break;
-                                }
 
                                 bit_idx = __ffs(bits);
 
@@ -1117,22 +1112,23 @@ static void __xen_evtchn_do_upcall(void)
                                                 generic_handle_irq_desc(irq, desc);
                                 }
 
-                                /*
-                                 * If this is the final port processed, we'll
-                                 * pick up here+1 next time.
-                                 */
-                                __this_cpu_write(last_word_idx, word_idx);
-                                __this_cpu_write(last_bit_idx, bit_idx);
-                        } while (bit_idx != BITS_PER_LONG - 1);
+                                bit_idx = (bit_idx + 1) % BITS_PER_LONG;
+
+                                /* Next caller starts at last processed + 1 */
+                                __this_cpu_write(current_word_idx,
+                                                 bit_idx ? word_idx :
+                                                 (word_idx+1) % BITS_PER_LONG);
+                                __this_cpu_write(current_bit_idx, bit_idx);
+                        } while (bit_idx != 0);
 
                         pending_bits = active_evtchns(cpu, s, word_idx);
 
-                        /*
-                         * We handled all ports, so we can clear the
-                         * selector bit.
-                         */
+                        /* If we handled all ports, clear the selector bit. */
                         if (pending_bits == 0)
                                 pending_words &= ~(1UL << word_idx);
+
+                        word_idx = (word_idx + 1) % BITS_PER_LONG;
+                        bit_idx = 0;
                 }
 
                 BUG_ON(!irqs_disabled());