[Qemu-devel] [PATCH 3/3] tcg: Avoid bouncing tb_lock between tb_gen_code() and tb_add_jump()

[Sergey Fedorov <sergey.fedorov@linaro.org>]

From: Sergey Fedorov <serge.fdrv@gmail.com>

Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
---
 cpu-exec.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/cpu-exec.c b/cpu-exec.c
index dd0bd5007701..54c935039592 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -295,7 +295,8 @@ static TranslationBlock *tb_find_slow(CPUState *cpu,
 
         /* mmap_lock is needed by tb_gen_code, and mmap_lock must be
          * taken outside tb_lock. As system emulation is currently
-         * single threaded the locks are NOPs.
+         * single threaded the locks are NOPs. Both locks are to be
+         * released at the end of tb_find_fast().
          */
         mmap_lock();
         tb_lock();
@@ -308,9 +309,6 @@ static TranslationBlock *tb_find_slow(CPUState *cpu,
             /* if no translated code available, then translate it now */
             tb = tb_gen_code(cpu, pc, cs_base, flags, 0);
         }
-
-        tb_unlock();
-        mmap_unlock();
     }
 
     /* We add the TB in the virtual pc hash table for the fast lookup */
@@ -354,10 +352,15 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu,
 #endif
     /* See if we can patch the calling TB. */
     if (*last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) {
-        tb_lock();
+        if (!tb_lock_locked()) {
+            tb_lock();
+        }
         tb_add_jump(*last_tb, tb_exit, tb);
-        tb_unlock();
     }
+
+    tb_lock_reset();
+    mmap_lock_reset();
+
     return tb;
 }
 
-- 
1.9.1