Merge branch 'MTX-3262-single-instance-guard' into 'master'

MTX-3262 mpower: lockfile rewrite for interprocess communication safety

See merge request !16

2 files changed, 30 insertions, 70 deletions

diff --git a/include/mts/MTS_IO_LockFile.h b/include/mts/MTS_IO_LockFile.h
index 730cf3c..22e641b 100644
--- a/include/mts/MTS_IO_LockFile.h
+++ b/include/mts/MTS_IO_LockFile.h
@@ -34,11 +34,8 @@
 
 namespace MTS {
     namespace IO {
-
         class LockFile : MTS::NonCopyable {
-
             public:
-
                 LockFile(const std::string& sFilePath);
                 virtual ~LockFile();
 
@@ -46,11 +43,10 @@ namespace MTS {
                 void unlock();
                 bool isLocked();
 
-            protected:
-
             private:
                 std::string m_sFile;
                 int m_iLockFd;
+                int m_iLockErr;
         };
 
     }
diff --git a/src/MTS_IO_LockFile.cpp b/src/MTS_IO_LockFile.cpp
index b74ba73..7f84f42 100644
--- a/src/MTS_IO_LockFile.cpp
+++ b/src/MTS_IO_LockFile.cpp
@@ -18,9 +18,9 @@
  *
  */
 
-/*! 
+/*!
  \file MTS_IO_LockFile.cpp
- \brief A brief description 
+ \brief A brief description
  \date Oct 8, 2014
  \author sgodinez
 
@@ -29,13 +29,7 @@
 
 #include <mts/MTS_IO_LockFile.h>
 #include <mts/MTS_Timer.h>
-#include <mts/MTS_Logger.h>
-#include <mts/MTS_System.h>
-#include <mts/MTS_Text.h>
 #include <sys/file.h>
-#include <sys/stat.h>
-#include <errno.h>
-#include <string.h>
 #include <unistd.h>
 
 using namespace MTS::IO;
@@ -43,79 +37,49 @@ using namespace MTS::IO;
 LockFile::LockFile(const std::string& sFile)
 : m_sFile(sFile)
 , m_iLockFd(-1)
+, m_iLockErr(-1)
 {
-
 }
 
-LockFile::~LockFile() {
+LockFile::~LockFile()
+{
     unlock();
 }
 
-bool LockFile::lock(uint32_t attemptMillis) {
-    if(isLocked()) {
+bool LockFile::lock(uint32_t attemptMillis)
+{
+    if (isLocked()) {
         return true;
     }
 
-    MTS::Timer timer;
-
-    timer.start();
-    while(timer.getMillis() < attemptMillis) {
-        m_iLockFd =::open(m_sFile.c_str(), O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
-        if (m_iLockFd < 0) {
-            // device already locked -> bail out
-            printWarning("LockFile| Failed to Lock [%s] [%d][%s]", m_sFile.c_str(), errno, strerror(errno));
-
-            //Check if lock file's process still exists
-            std::string sResult;
-            if(MTS::System::readFile(m_sFile, sResult) == 0 && sResult.size() > 0) {
-                struct stat sts;
-                std::string sProc = "/proc/" + MTS::Text::trim(sResult);
-                if (stat(sProc.c_str(), &sts) == -1 && errno == ENOENT) {
-                    printWarning("LockFile| Current Lock's Process [%s] does not exist.  Removing lock.", sResult.c_str());
-                    // process doesn't exist -> remove file
-                    ::unlink(m_sFile.c_str());
-                }
-            }
-
-        } else {
-            //TODO: Investigate using flock in addition to minicom-style lock : flock(m_iLockFd, LOCK_EX | LOCK_NB);
-
-            // %4d to make concurrent mgetty (if any) happy.
-            // Mgetty treats 4-bytes lock files as binary,
-            // not text, PID. Making 5+ char file. Brrr...
-            char buf[256] = {0};
-            size_t written = 0;
-
-            sprintf(buf, "%4d\n", getpid());
-            size_t wsize = strlen(buf);
-
-            written = write(m_iLockFd, buf, wsize);
-
-            if (wsize != written) {
-                printError("LockFile| Error writing to lock file [%s] [%d][%s]", m_sFile.c_str(), errno, strerror(errno));
-                close(m_iLockFd);
-                return false;
-            }
-            else {
-                close(m_iLockFd);
+    m_iLockFd = ::open(m_sFile.c_str(), O_CREAT | O_RDWR, 0644);
+    if (m_iLockFd >= 0) {
+        MTS::Timer timer;
+        timer.start();
+        while (timer.getMillis() < attemptMillis) {
+            m_iLockErr = ::flock(m_iLockFd, LOCK_EX | LOCK_NB);
+            if (m_iLockErr == 0) {
                 return true;
+            } else if (errno != EWOULDBLOCK) {
+                break;
             }
+            ::usleep(((rand() % 10) + 1) * 100000); //Sleep from 100ms to 1 Second
         }
-        uint32_t randomSleepTime = ((rand() % 10) + 1) * 100000; //Sleep from 100ms to 1 Second
-        ::usleep(randomSleepTime);
+        ::close(m_iLockFd);
     }
+    m_iLockFd = -1;
     return false;
 }
 
-void LockFile::unlock() {
-    if(isLocked()) {
-        ::unlink(m_sFile.c_str());
-        //TODO: flock cleanup : flock(m_iLockFd, LOCK_UN);
-        m_iLockFd = -1;
-    }
+void LockFile::unlock()
+{
+    ::flock(m_iLockFd, LOCK_UN);
+    ::close(m_iLockFd);
+    m_iLockFd = -1;
+    m_iLockErr = -1;
 }
 
-bool LockFile::isLocked() {
-    return m_iLockFd >= 0;
+bool LockFile::isLocked()
+{
+    return m_iLockErr == 0;
 }
-