[Qemu-devel] [RFC v1 10/11] tcg: grab iothread lock in cpu-exec interrupt handling

["Alex Bennée" <alex.bennee@linaro.org>]

From: "Emilio G. Cota" <cota@braap.org>

Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

---
v1 (ajb)
 - pulled from emilio/mttcg series
---
 cpu-exec.c        | 33 +++++++++++++++++++++++++++------
 include/qom/cpu.h |  1 +
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/cpu-exec.c b/cpu-exec.c
index 76891fd..6acaf25 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -351,6 +351,29 @@ static void cpu_handle_debug_exception(CPUState *cpu)
     cc->debug_excp_handler(cpu);
 }
 
+#ifdef CONFIG_SOFTMMU
+static inline void cpu_exit_loop_lock(CPUState *cpu)
+{
+    qemu_mutex_lock_iothread();
+    cpu->cpu_loop_exit_locked = true;
+}
+
+static inline void cpu_exit_loop_lock_reset(CPUState *cpu)
+{
+    if (cpu->cpu_loop_exit_locked) {
+        cpu->cpu_loop_exit_locked = false;
+        qemu_mutex_unlock_iothread();
+    }
+}
+
+#else
+static inline void cpu_exit_loop_lock(CPUState *cpu)
+{ }
+
+static inline void cpu_exit_loop_lock_reset(CPUState *cpu)
+{ }
+#endif
+
 /* main execution loop */
 
 int cpu_exec(CPUState *cpu)
@@ -450,12 +473,7 @@ int cpu_exec(CPUState *cpu)
             for(;;) {
                 interrupt_request = cpu->interrupt_request;
                 if (unlikely(interrupt_request)) {
-                    /* FIXME: this needs to take the iothread lock.
-                     * For this we need to find all places in
-                     * cc->cpu_exec_interrupt that can call cpu_loop_exit,
-                     * and call qemu_unlock_iothread_mutex() there.  Else,
-                     * add a flag telling cpu_loop_exit() to unlock it.
-                     */
+                    cpu_exit_loop_lock(cpu);
 
                     if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
                         /* Mask out external interrupts for this step. */
@@ -510,6 +528,8 @@ int cpu_exec(CPUState *cpu)
                         next_tb = 0;
                     }
 
+                    cpu_exit_loop_lock_reset(cpu);
+
                 }
                 if (unlikely(cpu->exit_request
                              || replay_has_interrupt())) {
@@ -630,6 +650,7 @@ int cpu_exec(CPUState *cpu)
 
             cpu->can_do_io = 1;
             tb_lock_reset();
+            cpu_exit_loop_lock_reset(cpu);
         }
     } /* for(;;) */
 
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index d6cb7b8..954d97d 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -295,6 +295,7 @@ struct CPUState {
     bool crash_occurred;
     bool exit_request;
     bool tb_invalidated_flag;
+    bool cpu_loop_exit_locked;
     uint32_t interrupt_request;
     int singlestep_enabled;
     int64_t icount_extra;
-- 
2.7.3