Fix #373: Correct mutex around log file write

The mutex for the log file write during the WriteLogFileCmd
excution was held longer than it should have been.

This lock must *NOT* be held during EVS_SendEvent, as this
will cause deadlock.

This moves the mutex to protect only the area that actually
accesses the log data, and it moves all send event calls
to be AFTER the mutex is released.

fsw/cfe-core/src/evs/cfe_evs_log.c

@@ -167,9 +167,6 @@ int32 CFE_EVS_WriteLogDataFileCmd(const CFE_EVS_WriteLogDataFile_t *data)
     }
     else
     {
-        /* Serialize access to event log control variables */
-        OS_MutSemTake(CFE_EVS_GlobalData.EVS_SharedDataMutexID);
-
         /* Copy the commanded filename into local buffer to ensure size limitation and to allow for modification */
         CFE_SB_MessageStringGet(LogFilename, (const char *)CmdPtr->LogFilename, CFE_PLATFORM_EVS_DEFAULT_LOG_FILE,
                 OS_MAX_PATH_LEN, sizeof(CmdPtr->LogFilename));
@@ -198,6 +195,9 @@ int32 CFE_EVS_WriteLogDataFileCmd(const CFE_EVS_WriteLogDataFile_t *data)
 
             if (BytesWritten == sizeof(LogFileHdr))
             {
+                /* Serialize access to event log control variables */
+                OS_MutSemTake(CFE_EVS_GlobalData.EVS_SharedDataMutexID);
+
                 /* Is the log full? -- Doesn't matter if wrap mode is enabled */
                 if (CFE_EVS_GlobalData.EVS_LogPtr->LogCount == CFE_PLATFORM_EVS_LOG_MAX)
                 {
@@ -228,13 +228,12 @@ int32 CFE_EVS_WriteLogDataFileCmd(const CFE_EVS_WriteLogDataFile_t *data)
                     }
                     else
                     {
-                        EVS_SendEvent(CFE_EVS_ERR_WRLOGFILE_EID, CFE_EVS_EventType_ERROR,
-                                "Write Log File Command Error: OS_write = 0x%08X, filename = %s",
-                                (unsigned int)BytesWritten, LogFilename);
                         break;
                     }
                 }
 
+                OS_MutSemGive(CFE_EVS_GlobalData.EVS_SharedDataMutexID);
+
                 /* Process command handler success result */
                 if (i == CFE_EVS_GlobalData.EVS_LogPtr->LogCount)
                 {
@@ -243,13 +242,17 @@ int32 CFE_EVS_WriteLogDataFileCmd(const CFE_EVS_WriteLogDataFile_t *data)
                             (int)CFE_EVS_GlobalData.EVS_LogPtr->LogCount, LogFilename);
                     Result = CFE_SUCCESS;
                 }
+                else
+                {
+                    EVS_SendEvent(CFE_EVS_ERR_WRLOGFILE_EID, CFE_EVS_EventType_ERROR,
+                            "Write Log File Command Error: OS_write = 0x%08X, filename = %s",
+                            (unsigned int)BytesWritten, LogFilename);
+                }
             }
 
             OS_close(LogFileHandle);
         }
 
-        OS_MutSemGive(CFE_EVS_GlobalData.EVS_SharedDataMutexID);
-
     }
 
     return(Result);