Revert "MTX-3262 mpower: lockfile rewrite for interprocess communication safety"

This reverts commit bab7e498b6dc31b6967a59fd728c5e5fe59d485c.

1 files changed, 65 insertions, 29 deletions

diff --git a/src/MTS_IO_LockFile.cpp b/src/MTS_IO_LockFile.cpp
index 7f84f42..b74ba73 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
 
@@ -29,7 +29,13 @@
 
 #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;
@@ -37,49 +43,79 @@ 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;
     }
 
-    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) {
+    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);
                 return true;
-            } else if (errno != EWOULDBLOCK) {
-                break;
             }
-            ::usleep(((rand() % 10) + 1) * 100000); //Sleep from 100ms to 1 Second
         }
-        ::close(m_iLockFd);
+        uint32_t randomSleepTime = ((rand() % 10) + 1) * 100000; //Sleep from 100ms to 1 Second
+        ::usleep(randomSleepTime);
     }
-    m_iLockFd = -1;
     return false;
 }
 
-void LockFile::unlock()
-{
-    ::flock(m_iLockFd, LOCK_UN);
-    ::close(m_iLockFd);
-    m_iLockFd = -1;
-    m_iLockErr = -1;
+void LockFile::unlock() {
+    if(isLocked()) {
+        ::unlink(m_sFile.c_str());
+        //TODO: flock cleanup : flock(m_iLockFd, LOCK_UN);
+        m_iLockFd = -1;
+    }
 }
 
-bool LockFile::isLocked()
-{
-    return m_iLockErr == 0;
+bool LockFile::isLocked() {
+    return m_iLockFd >= 0;
 }
+