From fb5fdb17dbe5a689d8d277e2eb4802c0553789a8 Mon Sep 17 00:00:00 2001
From: counterpoint <counterpoint@aliro.org>
Date: Fri, 8 Jan 2016 12:19:29 +0000
Subject: [PATCH] Switch bitmask_clear to be locking and offer
 bitmask_clear_without_spinlock for non-locking version, in response to review
 comments. Revert poll.c to use bitmask_clear (with locking) and amend dcb.c
 to use the non-locking version and to take advantage of the return of an
 indication of whether the whole bitmask is then clearn.

---
 server/core/dcb.c          |  6 ++----
 server/core/gwbitmask.c    | 10 +++++-----
 server/core/poll.c         |  2 +-
 server/include/gwbitmask.h |  2 +-
 4 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/server/core/dcb.c b/server/core/dcb.c
index 322a27163..ced6bc894 100644
--- a/server/core/dcb.c
+++ b/server/core/dcb.c
@@ -489,9 +489,7 @@ dcb_process_zombies(int threadid)
         else
         {
 
-            bitmask_clear(&zombiedcb->memdata.bitmask, threadid);
-
-            if (bitmask_isallclear(&zombiedcb->memdata.bitmask))
+            if (bitmask_clear_without_spinlock(&zombiedcb->memdata.bitmask))
             {
                 /**
                  * Remove the DCB from the zombie queue
@@ -1736,7 +1734,7 @@ dcb_drain_writeq_SSL(DCB *dcb)
     return n;
 }
 
-/** 
+/**
  * Removes dcb from poll set, and adds it to zombies list. As a consequence,
  * dcb first moves to DCB_STATE_NOPOLLING, and then to DCB_STATE_ZOMBIE state.
  * At the end of the function state may not be DCB_STATE_ZOMBIE because once
diff --git a/server/core/gwbitmask.c b/server/core/gwbitmask.c
index 9ba51d347..ce49c8bd6 100644
--- a/server/core/gwbitmask.c
+++ b/server/core/gwbitmask.c
@@ -140,14 +140,14 @@ bitmask_set(GWBITMASK *bitmask, int bit)
  * Note that this function does not lock the bitmask, but assumes that
  * it is under the exclusive control of the caller.  If you want to use the
  * bitmask spinlock to protect access while clearing the bit, then call
- * the alternative bitmask_clear_with_lock.
+ * the alternative bitmask_clear.
  *
  * @param bitmask       Pointer the bitmask
  * @param bit           Bit to clear
  * @return int          1 if the bitmask is all clear after the operation, else 0.
  */
 int
-bitmask_clear(GWBITMASK *bitmask, int bit)
+bitmask_clear_without_spinlock(GWBITMASK *bitmask, int bit)
 {
     unsigned char *ptr = bitmask->bits;
     int i;
@@ -174,19 +174,19 @@ bitmask_clear(GWBITMASK *bitmask, int bit)
 
 /**
  * Clear the bit at the specified bit position in the bitmask using a spinlock.
- * See bitmask_clear for more details
+ * See bitmask_clear_without_spinlock for more details
  *
  * @param bitmask       Pointer the bitmask
  * @param bit           Bit to clear
  * @return int          1 if the bitmask is all clear after the operation, else 0
  */
 int
-bitmask_clear_with_lock(GWBITMASK *bitmask, int bit)
+bitmask_clear(GWBITMASK *bitmask, int bit)
 {
     int result;
 
     spinlock_acquire(&bitmask->lock);
-    result = bitmask_clear(bitmask, bit);
+    result = bitmask_clear_without_spinlock(bitmask, bit);
     spinlock_release(&bitmask->lock);
     return result;
 }
diff --git a/server/core/poll.c b/server/core/poll.c
index 569ee6139..4155bc641 100644
--- a/server/core/poll.c
+++ b/server/core/poll.c
@@ -725,7 +725,7 @@ poll_waitevents(void *arg)
             {
                 thread_data[thread_id].state = THREAD_STOPPED;
             }
-            bitmask_clear_with_lock(&poll_mask, thread_id);
+            bitmask_clear(&poll_mask, thread_id);
             /** Release mysql thread context */
             mysql_thread_end();
             return;
diff --git a/server/include/gwbitmask.h b/server/include/gwbitmask.h
index 71620f5fd..5df50114f 100644
--- a/server/include/gwbitmask.h
+++ b/server/include/gwbitmask.h
@@ -52,7 +52,7 @@ extern void bitmask_init(GWBITMASK *);
 extern void bitmask_free(GWBITMASK *);
 extern void bitmask_set(GWBITMASK *, int);
 extern int  bitmask_clear(GWBITMASK *, int);
-extern int  bitmask_clear_with_lock(GWBITMASK *, int);
+extern int  bitmask_clear_without_spinlock(GWBITMASK *, int);
 extern int  bitmask_isset(GWBITMASK *, int);
 extern int  bitmask_isallclear(GWBITMASK *);
 extern void bitmask_copy(GWBITMASK *, GWBITMASK *);