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make LocSharedLock::mRef ops atomic

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The current share() and drop() calls are not thread
safe, which can cause memory heap correuption. This
changes the read / write ops to be atomic.

Change-Id: Ic241d4573bdf2e58c4e264e97bd41b56f882c791
CRs-Fixed: 975372
This commit is contained in:
Kevin Tang 2016-02-11 14:50:58 -08:00 committed by Gerrit - the friendly Code Review server
parent 41961e47d5
commit 411951c341
1 changed files with 4 additions and 3 deletions
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7
utils/LocSharedLock.h
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@ -30,6 +30,7 @@
#define __LOC_SHARED_LOCK__
#include <stddef.h>
#include <cutils/atomic.h>
#include <pthread.h>
// This is a utility created for use cases such that there are more than
@ -39,16 +40,16 @@
// this share lock's share() method has to be called, so that the obj
// can maintain an accurate client count.
class LocSharedLock {
uint32_t mRef;
volatile int32_t mRef;
pthread_mutex_t mMutex;
inline ~LocSharedLock() { pthread_mutex_destroy(&mMutex); }
public:
// first client to create this LockSharedLock
inline LocSharedLock() : mRef(1) { pthread_mutex_init(&mMutex, NULL); }
// following client(s) are to *share()* this lock created by the first client
inline LocSharedLock* share() { mRef++; return this; }
inline LocSharedLock* share() { android_atomic_inc(&mRef); return this; }
// whe a client no longer needs this shared lock, drop() shall be called.
inline void drop() { if (0 == --mRef) delete this; }
inline void drop() { if (1 == android_atomic_dec(&mRef)) delete this; }
// locking the lock to enter critical section
inline void lock() { pthread_mutex_lock(&mMutex); }
// unlocking the lock to leave the critical section