Bug#13898343 THREAD LOOPS ENDLESSLY IN LF_PINBOX_PUT_PINS WHILE HOLDING

LOCK_THREAD_COUNT

When using the performance schema file io instrumentation in MySQL 5.5,
a thread would loop forever inside lf_pinbox_put_pins, when disconnecting.
It would also hold LOCK_thread_count while doing so, effectively killing the
server.

The root cause of the loop in lf_pinbox_put_pins() is a leak of LF_PINS,
when used with the filename_hash LF_HASH table in the performance schema.

This fix contains the following changes:

1)
Added the missing call to lf_hash_search_unpin(), to prevent the leak.

2)
In mysys/lf_alloc-pin.c, there was some extra debugging code
(MY_LF_EXTRA_DEBUG) written to detect precisely this kind of issues,
but it was never used.
Replaced MY_LF_EXTRA_DEBUG with DBUG_OFF, so that leaks similar to this one
can be always detected in regular debug builds.

3)
Backported the fix for the following bug, from 5.6 to 5.5:
Bug#13417446 - 63339: INCORRECT FILE PATH IN PEFORMANCE_SCHEMA ON WINDOWS

1 files changed, 5 insertions, 2 deletions

diff --git a/mysys/lf_alloc-pin.c b/mysys/lf_alloc-pin.c
index 22887d17c07..7af87bca111 100644
--- a/mysys/lf_alloc-pin.c
+++ b/mysys/lf_alloc-pin.c
@@ -211,13 +211,16 @@ void _lf_pinbox_put_pins(LF_PINS *pins)
   LF_PINBOX *pinbox= pins->pinbox;
   uint32 top_ver, nr;
   nr= pins->link;
-#ifdef MY_LF_EXTRA_DEBUG
+
+#ifndef DBUG_OFF
   {
+    /* This thread should not hold any pin. */
     int i;
     for (i= 0; i < LF_PINBOX_PINS; i++)
       DBUG_ASSERT(pins->pin[i] == 0);
   }
-#endif
+#endif /* DBUG_OFF */
+
   /*
     XXX this will deadlock if other threads will wait for
     the caller to do something after _lf_pinbox_put_pins(),