msm: camera: memmgr: Remove the mutex lock for kref variable

kref operation is atmoic operation, so no need to use mutex
to protect it, and the cam_mem_put_cpu_buf is also called
in spinlock context, so we can't use mutex lock in this
function. This change removes the mutex lock for kref
variable protextion.

CRs-Fixed: 3786887
Change-Id: Ic05bdafacf06cde6a8d8dbae7512e5d22eb7f514
Signed-off-by: Depeng Shao <[email protected]>
(cherry picked from commit bb64b99c83b3bb6da0c241eda74ebe8a19b51840)

drivers/cam_req_mgr/cam_mem_mgr.c

@@ -340,7 +340,6 @@ static int32_t cam_mem_get_slot(void)
 	tbl.bufq[idx].release_deferred = false;
 	CAM_GET_TIMESTAMP((tbl.bufq[idx].timestamp));
 	mutex_init(&tbl.bufq[idx].q_lock);
-	mutex_init(&tbl.bufq[idx].ref_lock);
 	mutex_unlock(&tbl.m_lock);
 
 	return idx;
@@ -354,13 +353,10 @@ static void cam_mem_put_slot(int32_t idx)
 	tbl.bufq[idx].release_deferred = false;
 	tbl.bufq[idx].is_internal = false;
 	memset(&tbl.bufq[idx].timestamp, 0, sizeof(struct timespec64));
+	kref_init(&tbl.bufq[idx].krefcount);
+	kref_init(&tbl.bufq[idx].urefcount);
 	mutex_unlock(&tbl.bufq[idx].q_lock);
-	mutex_lock(&tbl.bufq[idx].ref_lock);
-	memset(&tbl.bufq[idx].krefcount, 0, sizeof(struct kref));
-	memset(&tbl.bufq[idx].urefcount, 0, sizeof(struct kref));
-	mutex_unlock(&tbl.bufq[idx].ref_lock);
 	mutex_destroy(&tbl.bufq[idx].q_lock);
-	mutex_destroy(&tbl.bufq[idx].ref_lock);
 	clear_bit(idx, tbl.bitmap);
 	mutex_unlock(&tbl.m_lock);
 }
@@ -539,17 +535,14 @@ int cam_mem_get_cpu_buf(int32_t buf_handle, uintptr_t *vaddr_ptr, size_t *len)
 		return -EINVAL;
 	}
 
-	mutex_lock(&tbl.bufq[idx].ref_lock);
 	if (tbl.bufq[idx].kmdvaddr && kref_get_unless_zero(&tbl.bufq[idx].krefcount)) {
 		*vaddr_ptr = tbl.bufq[idx].kmdvaddr;
 		*len = tbl.bufq[idx].len;
 	} else {
-		mutex_unlock(&tbl.bufq[idx].ref_lock);
 		CAM_ERR(CAM_MEM, "No KMD access requested, kmdvddr= %p, idx= %d, buf_handle= %d",
 			tbl.bufq[idx].kmdvaddr, idx, buf_handle);
 		return -EINVAL;
 	}
-	mutex_unlock(&tbl.bufq[idx].ref_lock);
 
 	return 0;
 }
@@ -1713,13 +1706,10 @@ static int cam_mem_mgr_cleanup_table(void)
 		tbl.bufq[i].is_internal = false;
 		memset(tbl.bufq[i].hdls_info, 0x0, tbl.max_hdls_info_size);
 		cam_mem_mgr_reset_presil_params(i);
+		kref_init(&tbl.bufq[i].krefcount);
+		kref_init(&tbl.bufq[i].urefcount);
 		mutex_unlock(&tbl.bufq[i].q_lock);
-		mutex_lock(&tbl.bufq[i].ref_lock);
-		memset(&tbl.bufq[i].krefcount, 0, sizeof(struct kref));
-		memset(&tbl.bufq[i].urefcount, 0, sizeof(struct kref));
-		mutex_unlock(&tbl.bufq[i].ref_lock);
 		mutex_destroy(&tbl.bufq[i].q_lock);
-		mutex_destroy(&tbl.bufq[i].ref_lock);
 	}
 
 	bitmap_zero(tbl.bitmap, tbl.bits);
@@ -1863,8 +1853,6 @@ static void cam_mem_util_unmap_wrapper(struct kref *kref)
 	}
 
 	cam_mem_util_unmap(idx);
-
-	mutex_destroy(&tbl.bufq[idx].ref_lock);
 }
 
 void cam_mem_put_cpu_buf(int32_t buf_handle)
@@ -1897,7 +1885,6 @@ void cam_mem_put_cpu_buf(int32_t buf_handle)
 		return;
 	}
 
-	mutex_lock(&tbl.bufq[idx].ref_lock);
 	kref_put(&tbl.bufq[idx].krefcount, cam_mem_util_unmap_dummy);
 
 	krefcount = kref_read(&tbl.bufq[idx].krefcount);
@@ -1930,11 +1917,6 @@ void cam_mem_put_cpu_buf(int32_t buf_handle)
 			"Unbalanced release Called buf_handle: %u, idx: %d",
 			tbl.bufq[idx].buf_handle, idx);
 	}
-	mutex_unlock(&tbl.bufq[idx].ref_lock);
-
-	if (unmap)
-		mutex_destroy(&tbl.bufq[idx].ref_lock);
-
 }
 EXPORT_SYMBOL(cam_mem_put_cpu_buf);
 
@@ -1979,7 +1961,6 @@ int cam_mem_mgr_release(struct cam_mem_mgr_release_cmd *cmd)
 
 	CAM_DBG(CAM_MEM, "Releasing hdl = %x, idx = %d", cmd->buf_handle, idx);
 
-	mutex_lock(&tbl.bufq[idx].ref_lock);
 	kref_put(&tbl.bufq[idx].urefcount, cam_mem_util_unmap_dummy);
 
 	urefcount = kref_read(&tbl.bufq[idx].urefcount);
@@ -2013,11 +1994,6 @@ int cam_mem_mgr_release(struct cam_mem_mgr_release_cmd *cmd)
 		tbl.bufq[idx].release_deferred = true;
 	}
 
-	mutex_unlock(&tbl.bufq[idx].ref_lock);
-
-	if (unmap)
-		mutex_destroy(&tbl.bufq[idx].ref_lock);
-
 	return rc;
 }
 

drivers/cam_req_mgr/cam_mem_mgr.h

@@ -88,7 +88,6 @@ struct cam_mem_buf_hw_hdl_info {
  * @presil_params:       Parameters specific to presil environment
  * @urefcount:           Reference counter to track whether the buffer is
  *                       mapped and in use by umd
- * @ref_lock:            Mutex lock for refcount
  */
 struct cam_mem_buf_queue {
 	struct dma_buf *dma_buf;
@@ -115,7 +114,6 @@ struct cam_mem_buf_queue {
 	struct cam_presil_dmabuf_params presil_params;
 #endif
 	struct kref urefcount;
-	struct mutex ref_lock;
 };
 
 /**