commit 4f9576bf48c5909782c12490e8a9faa974ae68d6
author Ruben Brunk <rubenbrunk@google.com> Fri Apr 10 17:26:56 2015 -0700
committer Ruben Brunk <rubenbrunk@google.com> Mon Apr 13 16:55:41 2015 -0700
tree 9392dc3ff4216fd7bfa4e41ea7838ec6570bfcf7
parent a8ca9157d21510fbd474bd31748f4fe0d4635dd7

camera: Fix client eviction/disconnect race.

- Add blocking wait in camera service connect call to
  prevent race when client has called disconnect while
  eviction of that client is taking place, resulting
  in early call of device initialization before all
  HAL resources are available.

Bug: 20038135
Change-Id: I7afc5bfa23612ba7f83293fa542ff983a5991230

services/camera/libcameraservice/utils/ClientManager.h

diff --git a/services/camera/libcameraservice/utils/ClientManager.h b/services/camera/libcameraservice/utils/ClientManager.h
index ad5486d..aa40a2d 100644
--- a/services/camera/libcameraservice/utils/ClientManager.h
+++ b/services/camera/libcameraservice/utils/ClientManager.h
@@ -17,7 +17,9 @@
 #ifndef ANDROID_SERVICE_UTILS_EVICTION_POLICY_MANAGER_H
 #define ANDROID_SERVICE_UTILS_EVICTION_POLICY_MANAGER_H
 
+#include <utils/Condition.h>
 #include <utils/Mutex.h>
+#include <utils/Timers.h>
 
 #include <algorithm>
 #include <utility>
@@ -263,6 +265,16 @@
      */
     std::shared_ptr<ClientDescriptor<KEY, VALUE>> get(const KEY& key) const;
 
+    /**
+     * Block until the given client is no longer in the active clients list, or the timeout
+     * occurred.
+     *
+     * Returns NO_ERROR if this succeeded, -ETIMEDOUT on a timeout, or a negative error code on
+     * failure.
+     */
+    status_t waitUntilRemoved(const std::shared_ptr<ClientDescriptor<KEY, VALUE>> client,
+            nsecs_t timeout) const;
+
 protected:
     ~ClientManager();
 
@@ -284,6 +296,7 @@
     int64_t getCurrentCostLocked() const;
 
     mutable Mutex mLock;
+    mutable Condition mRemovedCondition;
     int32_t mMaxCost;
     // LRU ordered, most recent at end
     std::vector<std::shared_ptr<ClientDescriptor<KEY, VALUE>>> mClients;
@@ -430,6 +443,7 @@
         }), mClients.end());
 
     mClients.push_back(client);
+    mRemovedCondition.broadcast();
 
     return evicted;
 }
@@ -487,6 +501,7 @@
 void ClientManager<KEY, VALUE>::removeAll() {
     Mutex::Autolock lock(mLock);
     mClients.clear();
+    mRemovedCondition.broadcast();
 }
 
 template<class KEY, class VALUE>
@@ -505,6 +520,39 @@
             return false;
         }), mClients.end());
 
+    mRemovedCondition.broadcast();
+    return ret;
+}
+
+template<class KEY, class VALUE>
+status_t ClientManager<KEY, VALUE>::waitUntilRemoved(
+        const std::shared_ptr<ClientDescriptor<KEY, VALUE>> client,
+        nsecs_t timeout) const {
+    status_t ret = NO_ERROR;
+    Mutex::Autolock lock(mLock);
+
+    bool isRemoved = false;
+
+    // Figure out what time in the future we should hit the timeout
+    nsecs_t failTime = systemTime(SYSTEM_TIME_MONOTONIC) + timeout;
+
+    while (!isRemoved) {
+        isRemoved = true;
+        for (const auto& i : mClients) {
+            if (i == client) {
+                isRemoved = false;
+            }
+        }
+
+        if (!isRemoved) {
+            ret = mRemovedCondition.waitRelative(mLock, timeout);
+            if (ret != NO_ERROR) {
+                break;
+            }
+            timeout = failTime - systemTime(SYSTEM_TIME_MONOTONIC);
+        }
+    }
+
     return ret;
 }
 
@@ -520,6 +568,7 @@
             }
             return false;
         }), mClients.end());
+    mRemovedCondition.broadcast();
 }
 
 template<class KEY, class VALUE>