diff --git a/hal/audio_hw.c b/hal/audio_hw.c
index 8b0bf97..42bbc59 100644
--- a/hal/audio_hw.c
+++ b/hal/audio_hw.c
@@ -832,20 +832,14 @@
         return -EINVAL;
     }
 
-    /* 1. Close the PCM device first */
-    if (in->pcm) {
-        pcm_close(in->pcm);
-        in->pcm = NULL;
-    }
-
-    /* 2. Disable stream specific mixer controls */
+    /* 1. Disable stream specific mixer controls */
     in_snd_device = adev->cur_in_snd_device;
     disable_audio_route(adev->audio_route, in->usecase, in_snd_device);
     audio_route_update_mixer(adev->audio_route);
 
     remove_usecase_from_list(adev, in->usecase);
 
-    /* 3. Disable the tx device */
+    /* 2. Disable the tx device */
     select_devices(adev);
 
     ALOGD("%s: exit: status(%d)", __func__, ret);
@@ -940,20 +934,14 @@
         return -EINVAL;
     }
 
-    /* 1. Close the PCM device first */
-    if (out->pcm) {
-        pcm_close(out->pcm);
-        out->pcm = NULL;
-    }
-
-    /* 2. Get and set stream specific mixer controls */
+    /* 1. Get and set stream specific mixer controls */
     out_snd_device = adev->cur_out_snd_device;
     disable_audio_route(adev->audio_route, out->usecase, out_snd_device);
     audio_route_update_mixer(adev->audio_route);
 
     remove_usecase_from_list(adev, uc_info->id);
 
-    /* 3. Disable the rx device */
+    /* 2. Disable the rx device */
     adev->out_device = get_active_out_devices(adev, out->usecase);
     adev->out_device |= get_voice_call_out_device(adev);
     ret = select_devices(adev);
@@ -1254,15 +1242,19 @@
     struct stream_out *out = (struct stream_out *)stream;
     struct audio_device *adev = out->dev;
     ALOGD("%s: enter: usecase(%d)", __func__, out->usecase);
-    pthread_mutex_lock(&out->dev->lock);
     pthread_mutex_lock(&out->lock);
 
     if (!out->standby) {
         out->standby = true;
+        if (out->pcm) {
+            pcm_close(out->pcm);
+            out->pcm = NULL;
+        }
+        pthread_mutex_lock(&adev->lock);
         stop_output_stream(out);
+        pthread_mutex_unlock(&adev->lock);
     }
     pthread_mutex_unlock(&out->lock);
-    pthread_mutex_unlock(&out->dev->lock);
     ALOGD("%s: exit", __func__);
     return 0;
 }
@@ -1286,8 +1278,8 @@
     ret = str_parms_get_str(parms, AUDIO_PARAMETER_STREAM_ROUTING, value, sizeof(value));
     if (ret >= 0) {
         val = atoi(value);
-        pthread_mutex_lock(&adev->lock);
         pthread_mutex_lock(&out->lock);
+        pthread_mutex_lock(&adev->lock);
 
         if (adev->mode == AUDIO_MODE_IN_CALL && !adev->in_call && (val != 0)) {
             adev->out_device = get_active_out_devices(adev, out->usecase) | val;
@@ -1307,8 +1299,8 @@
             out->devices = val;
         }
 
-        pthread_mutex_unlock(&out->lock);
         pthread_mutex_unlock(&adev->lock);
+        pthread_mutex_unlock(&out->lock);
     }
     str_parms_destroy(parms);
     ALOGD("%s: exit: code(%d)", __func__, ret);
@@ -1374,21 +1366,16 @@
     struct audio_device *adev = out->dev;
     int i, ret = -1;
 
-    /* acquiring hw device mutex systematically is useful if a low priority thread is waiting
-     * on the output stream mutex - e.g. executing select_mode() while holding the hw device
-     * mutex
-     */
-    pthread_mutex_lock(&adev->lock);
     pthread_mutex_lock(&out->lock);
     if (out->standby) {
+        pthread_mutex_lock(&adev->lock);
         ret = start_output_stream(out);
+        pthread_mutex_unlock(&adev->lock);
         if (ret != 0) {
-            pthread_mutex_unlock(&adev->lock);
             goto exit;
         }
         out->standby = false;
     }
-    pthread_mutex_unlock(&adev->lock);
 
     if (out->pcm) {
         //ALOGV("%s: writing buffer (%d bytes) to pcm device", __func__, bytes);
@@ -1471,14 +1458,18 @@
     struct audio_device *adev = in->dev;
     int status = 0;
     ALOGD("%s: enter", __func__);
-    pthread_mutex_lock(&adev->lock);
     pthread_mutex_lock(&in->lock);
     if (!in->standby) {
         in->standby = true;
+        if (in->pcm) {
+            pcm_close(in->pcm);
+            in->pcm = NULL;
+        }
+        pthread_mutex_lock(&adev->lock);
         status = stop_input_stream(in);
+        pthread_mutex_unlock(&adev->lock);
     }
     pthread_mutex_unlock(&in->lock);
-    pthread_mutex_unlock(&adev->lock);
     ALOGD("%s: exit:  status(%d)", __func__, status);
     return status;
 }
@@ -1502,8 +1493,8 @@
 
     ret = str_parms_get_str(parms, AUDIO_PARAMETER_STREAM_INPUT_SOURCE, value, sizeof(value));
 
-    pthread_mutex_lock(&adev->lock);
     pthread_mutex_lock(&in->lock);
+    pthread_mutex_lock(&adev->lock);
     if (ret >= 0) {
         val = atoi(value);
         /* no audio source uses val == 0 */
@@ -1524,8 +1515,8 @@
         }
     }
 
-    pthread_mutex_unlock(&in->lock);
     pthread_mutex_unlock(&adev->lock);
+    pthread_mutex_unlock(&in->lock);
 
     str_parms_destroy(parms);
     ALOGD("%s: exit: status(%d)", __func__, ret);
@@ -1550,22 +1541,17 @@
     struct audio_device *adev = in->dev;
     int i, ret = -1;
 
-    /* acquiring hw device mutex systematically is useful if a low priority thread is waiting
-     * on the output stream mutex - e.g. executing select_mode() while holding the hw device
-     * mutex
-     */
     //ALOGV("%s: buffer(%p) bytes(%d)", __func__, buffer, bytes);
-    pthread_mutex_lock(&adev->lock);
     pthread_mutex_lock(&in->lock);
     if (in->standby) {
+      pthread_mutex_lock(&adev->lock);
         ret = start_input_stream(in);
+        pthread_mutex_unlock(&adev->lock);
         if (ret != 0) {
-            pthread_mutex_unlock(&adev->lock);
             goto exit;
         }
         in->standby = 0;
     }
-    pthread_mutex_unlock(&adev->lock);
 
     if (in->pcm) {
         ret = pcm_read(in->pcm, buffer, bytes);
diff --git a/hal/audio_hw.h b/hal/audio_hw.h
index 67f0b3a..0781688 100644
--- a/hal/audio_hw.h
+++ b/hal/audio_hw.h
@@ -138,7 +138,7 @@
 
 struct stream_out {
     struct audio_stream_out stream;
-    pthread_mutex_t lock;
+    pthread_mutex_t lock; /* see note below on mutex acquisition order */
     struct pcm_config config;
     struct pcm *pcm;
     int standby;
@@ -155,7 +155,7 @@
 
 struct stream_in {
     struct audio_stream_in stream;
-    pthread_mutex_t lock;
+    pthread_mutex_t lock; /* see note below on mutex acquisition order */
     struct pcm_config config;
     struct pcm *pcm;
     int standby;
@@ -198,7 +198,7 @@
 
 struct audio_device {
     struct audio_hw_device device;
-    pthread_mutex_t lock;
+    pthread_mutex_t lock; /* see note below on mutex acquisition order */
     struct mixer *mixer;
     audio_mode_t mode;
     audio_devices_t out_device;
@@ -243,6 +243,11 @@
     csd_stop_voice_t csd_stop_voice;
 };
 
+/*
+ * NOTE: when multiple mutexes have to be acquired, always take the
+ * stream_in or stream_out mutex first, followed by the audio_device mutex.
+ */
+
 struct pcm_config pcm_config_deep_buffer = {
     .channels = 2,
     .rate = DEFAULT_OUTPUT_SAMPLING_RATE,