[Qemu-devel] [RFC PATCH V6 02/18] replace spinlock by QemuMutex.

[fred . konrad]

From: KONRAD Frederic <address@hidden>

spinlock is only used in two cases:
  * cpu-exec.c: to protect TranslationBlock
  * mem_helper.c: for lock helper in target-i386 (which seems broken).

It's a pthread_mutex_t in user-mode so better using QemuMutex directly in this
case.
It allows as well to reuse tb_lock mutex of TBContext in case of multithread
TCG.

Signed-off-by: KONRAD Frederic <address@hidden>
---
 cpu-exec.c               | 15 +++++++++++----
 include/exec/exec-all.h  |  4 ++--
 linux-user/main.c        |  6 +++---
 target-i386/mem_helper.c | 16 +++++++++++++---
 tcg/i386/tcg-target.c    |  8 ++++++++
 5 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/cpu-exec.c b/cpu-exec.c
index 2ffeb6e..d6336d9 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -362,7 +362,9 @@ int cpu_exec(CPUArchState *env)
     SyncClocks sc;
 
     /* This must be volatile so it is not trashed by longjmp() */
+#if defined(CONFIG_USER_ONLY)
     volatile bool have_tb_lock = false;
+#endif
 
     if (cpu->halted) {
         if (!cpu_has_work(cpu)) {
@@ -480,8 +482,10 @@ int cpu_exec(CPUArchState *env)
                     cpu->exception_index = EXCP_INTERRUPT;
                     cpu_loop_exit(cpu);
                 }
-                spin_lock(&tcg_ctx.tb_ctx.tb_lock);
+#if defined(CONFIG_USER_ONLY)
+                qemu_mutex_lock(&tcg_ctx.tb_ctx.tb_lock);
                 have_tb_lock = true;
+#endif
                 tb = tb_find_fast(env);
                 /* Note: we do it here to avoid a gcc bug on Mac OS X when
                    doing it in tb_find_slow */
@@ -503,9 +507,10 @@ int cpu_exec(CPUArchState *env)
                     tb_add_jump((TranslationBlock *)(next_tb & ~TB_EXIT_MASK),
                                 next_tb & TB_EXIT_MASK, tb);
                 }
+#if defined(CONFIG_USER_ONLY)
                 have_tb_lock = false;
-                spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
-
+                qemu_mutex_unlock(&tcg_ctx.tb_ctx.tb_lock);
+#endif
                 /* cpu_interrupt might be called while translating the
                    TB, but before it is linked into a potentially
                    infinite loop and becomes env->current_tb. Avoid
@@ -572,10 +577,12 @@ int cpu_exec(CPUArchState *env)
 #ifdef TARGET_I386
             x86_cpu = X86_CPU(cpu);
 #endif
+#if defined(CONFIG_USER_ONLY)
             if (have_tb_lock) {
-                spin_unlock(&tcg_ctx.tb_ctx.tb_lock);
+                qemu_mutex_unlock(&tcg_ctx.tb_ctx.tb_lock);
                 have_tb_lock = false;
             }
+#endif
         }
     } /* for(;;) */
 
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 2573e8c..44f3336 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -176,7 +176,7 @@ struct TranslationBlock {
     struct TranslationBlock *jmp_first;
 };
 
-#include "exec/spinlock.h"
+#include "qemu/thread.h"
 
 typedef struct TBContext TBContext;
 
@@ -186,7 +186,7 @@ struct TBContext {
     TranslationBlock *tb_phys_hash[CODE_GEN_PHYS_HASH_SIZE];
     int nb_tbs;
     /* any access to the tbs or the page table must use this lock */
-    spinlock_t tb_lock;
+    QemuMutex tb_lock;
 
     /* statistics */
     int tb_flush_count;
diff --git a/linux-user/main.c b/linux-user/main.c
index c855bcc..bce3a98 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -107,7 +107,7 @@ static int pending_cpus;
 /* Make sure everything is in a consistent state for calling fork().  */
 void fork_start(void)
 {
-    pthread_mutex_lock(&tcg_ctx.tb_ctx.tb_lock);
+    qemu_mutex_lock(&tcg_ctx.tb_ctx.tb_lock);
     pthread_mutex_lock(&exclusive_lock);
     mmap_fork_start();
 }
@@ -129,11 +129,11 @@ void fork_end(int child)
         pthread_mutex_init(&cpu_list_mutex, NULL);
         pthread_cond_init(&exclusive_cond, NULL);
         pthread_cond_init(&exclusive_resume, NULL);
-        pthread_mutex_init(&tcg_ctx.tb_ctx.tb_lock, NULL);
+        qemu_mutex_init(&tcg_ctx.tb_ctx.tb_lock);
         gdbserver_fork((CPUArchState *)thread_cpu->env_ptr);
     } else {
         pthread_mutex_unlock(&exclusive_lock);
-        pthread_mutex_unlock(&tcg_ctx.tb_ctx.tb_lock);
+        qemu_mutex_unlock(&tcg_ctx.tb_ctx.tb_lock);
     }
 }
 
diff --git a/target-i386/mem_helper.c b/target-i386/mem_helper.c
index 1aec8a5..7106cc3 100644
--- a/target-i386/mem_helper.c
+++ b/target-i386/mem_helper.c
@@ -23,17 +23,27 @@
 
 /* broken thread support */
 
-static spinlock_t global_cpu_lock = SPIN_LOCK_UNLOCKED;
+#if defined(CONFIG_USER_ONLY)
+QemuMutex global_cpu_lock;
 
 void helper_lock(void)
 {
-    spin_lock(&global_cpu_lock);
+    qemu_mutex_lock(&global_cpu_lock);
 }
 
 void helper_unlock(void)
 {
-    spin_unlock(&global_cpu_lock);
+    qemu_mutex_unlock(&global_cpu_lock);
 }
+#else
+void helper_lock(void)
+{
+}
+
+void helper_unlock(void)
+{
+}
+#endif
 
 void helper_cmpxchg8b(CPUX86State *env, target_ulong a0)
 {
diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
index ff4d9cf..0d7c99c 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -24,6 +24,10 @@
 
 #include "tcg-be-ldst.h"
 
+#if defined(CONFIG_USER_ONLY)
+extern QemuMutex global_cpu_lock;
+#endif
+
 #ifndef NDEBUG
 static const char * const tcg_target_reg_names[TCG_TARGET_NB_REGS] = {
 #if TCG_TARGET_REG_BITS == 64
@@ -2342,6 +2346,10 @@ static void tcg_target_init(TCGContext *s)
     tcg_regset_set_reg(s->reserved_regs, TCG_REG_CALL_STACK);
 
     tcg_add_target_add_op_defs(x86_op_defs);
+
+#if defined(CONFIG_USER_ONLY)
+    qemu_mutex_init(global_cpu_lock);
+#endif
 }
 
 typedef struct {
-- 
1.9.0