Make FAT filesystem thread safe

Add lock and unlock calls to the FAT filesystem so it is thread safe.

Author: c1728p9

libraries/fs/fat/FATDirHandle.cpp

@@ -25,19 +25,22 @@
 
 using namespace mbed;
 
-FATDirHandle::FATDirHandle(const FATFS_DIR &the_dir) {
+FATDirHandle::FATDirHandle(const FATFS_DIR &the_dir, PlatformMutex * mutex): _mutex(mutex) {
     dir = the_dir;
 }
 
 int FATDirHandle::closedir() {
+    lock();
     int retval = f_closedir(&dir);
+    unlock();
     delete this;
     return retval;
 }
 
 struct dirent *FATDirHandle::readdir() {
     FILINFO finfo;
 
+    lock();
 #if _USE_LFN
     finfo.lfname = cur_entry.d_name;
     finfo.lfsize = sizeof(cur_entry.d_name);
@@ -47,33 +50,52 @@ struct dirent *FATDirHandle::readdir() {
 
 #if _USE_LFN
     if(res != 0 || finfo.fname[0]==0) {
+        unlock();
         return NULL;
     } else {
         if(cur_entry.d_name[0]==0) {
             // No long filename so use short filename.
             memcpy(cur_entry.d_name, finfo.fname, sizeof(finfo.fname));
         }
+        unlock();
         return &cur_entry;
     }
 #else
     if(res != 0 || finfo.fname[0]==0) {
+        unlock();
         return NULL;
     } else {
         memcpy(cur_entry.d_name, finfo.fname, sizeof(finfo.fname));
+        unlock();
         return &cur_entry;
     }
 #endif /* _USE_LFN */
 }
 
 void FATDirHandle::rewinddir() {
+    lock();
     dir.index = 0;
+    unlock();
 }
 
 off_t FATDirHandle::telldir() {
-    return dir.index;
+    lock();
+    off_t offset = dir.index;
+    unlock();
+    return offset;
 }
 
 void FATDirHandle::seekdir(off_t location) {
+    lock();
     dir.index = location;
+    unlock();
+}
+
+void FATDirHandle::lock() {
+    _mutex->lock();
+}
+
+void FATDirHandle::unlock() {
+    _mutex->unlock();
 }
 

libraries/fs/fat/FATDirHandle.h

@@ -23,19 +23,27 @@
 #define MBED_FATDIRHANDLE_H
 
 #include "DirHandle.h"
+#include "platform.h"
 
 using namespace mbed;
 
 class FATDirHandle : public DirHandle {
 
  public:
-    FATDirHandle(const FATFS_DIR &the_dir);
+    FATDirHandle(const FATFS_DIR &the_dir, PlatformMutex * mutex);
     virtual int closedir();
     virtual struct dirent *readdir();
     virtual void rewinddir();
     virtual off_t telldir();
     virtual void seekdir(off_t location);
 
+ protected:
+
+    virtual void lock();
+    virtual void unlock();
+
+    PlatformMutex * _mutex;
+
  private:
     FATFS_DIR dir;
     struct dirent cur_entry;

libraries/fs/fat/FATFileHandle.cpp

@@ -25,34 +25,42 @@
 
 #include "FATFileHandle.h"
 
-FATFileHandle::FATFileHandle(FIL fh) {
+FATFileHandle::FATFileHandle(FIL fh, PlatformMutex * mutex): _mutex(mutex) {
     _fh = fh;
 }
 
 int FATFileHandle::close() {
+    lock();
     int retval = f_close(&_fh);
+    unlock();
     delete this;
     return retval;
 }
 
 ssize_t FATFileHandle::write(const void* buffer, size_t length) {
+    lock();
     UINT n;
     FRESULT res = f_write(&_fh, buffer, length, &n);
     if (res) {
         debug_if(FFS_DBG, "f_write() failed: %d", res);
+        unlock();
         return -1;
     }
+    unlock();
     return n;
 }
 
 ssize_t FATFileHandle::read(void* buffer, size_t length) {
+    lock();
     debug_if(FFS_DBG, "read(%d)\n", length);
     UINT n;
     FRESULT res = f_read(&_fh, buffer, length, &n);
     if (res) {
         debug_if(FFS_DBG, "f_read() failed: %d\n", res);
+        unlock();
         return -1;
     }
+    unlock();
     return n;
 }
 
@@ -61,6 +69,7 @@ int FATFileHandle::isatty() {
 }
 
 off_t FATFileHandle::lseek(off_t position, int whence) {
+    lock();
     if (whence == SEEK_END) {
         position += _fh.fsize;
     } else if(whence==SEEK_CUR) {
@@ -69,22 +78,38 @@ off_t FATFileHandle::lseek(off_t position, int whence) {
     FRESULT res = f_lseek(&_fh, position);
     if (res) {
         debug_if(FFS_DBG, "lseek failed: %d\n", res);
+        unlock();
         return -1;
     } else {
         debug_if(FFS_DBG, "lseek OK, returning %i\n", _fh.fptr);
+        unlock();
         return _fh.fptr;
     }
 }
 
 int FATFileHandle::fsync() {
+    lock();
     FRESULT res = f_sync(&_fh);
     if (res) {
         debug_if(FFS_DBG, "f_sync() failed: %d\n", res);
+        unlock();
         return -1;
     }
+    unlock();
     return 0;
 }
 
 off_t FATFileHandle::flen() {
-    return _fh.fsize;
+    lock();
+    off_t size = _fh.fsize;
+    unlock();
+    return size;
+}
+
+void FATFileHandle::lock() {
+    _mutex->lock();
+}
+
+void FATFileHandle::unlock() {
+    _mutex->unlock();
 }

libraries/fs/fat/FATFileHandle.h

@@ -23,13 +23,14 @@
 #define MBED_FATFILEHANDLE_H
 
 #include "FileHandle.h"
+#include "platform.h"
 
 using namespace mbed;
 
 class FATFileHandle : public FileHandle {
 public:
 
-    FATFileHandle(FIL fh);
+    FATFileHandle(FIL fh, PlatformMutex * mutex);
     virtual int close();
     virtual ssize_t write(const void* buffer, size_t length);
     virtual ssize_t read(void* buffer, size_t length);
@@ -40,7 +41,11 @@ class FATFileHandle : public FileHandle {
 
 protected:
 
+    virtual void lock();
+    virtual void unlock();
+
     FIL _fh;
+    PlatformMutex * _mutex;
 
 };
 

libraries/fs/fat/FATFileSystem.cpp

@@ -27,6 +27,7 @@
 #include "FATFileSystem.h"
 #include "FATFileHandle.h"
 #include "FATDirHandle.h"
+#include "critical.h"
 
 DWORD get_fattime(void) {
     time_t rawtime;
@@ -41,33 +42,55 @@ DWORD get_fattime(void) {
 }
 
 FATFileSystem *FATFileSystem::_ffs[_VOLUMES] = {0};
+static PlatformMutex * mutex = NULL;
 
-FATFileSystem::FATFileSystem(const char* n) : FileSystemLike(n) {
+PlatformMutex * get_fat_mutex() {
+    PlatformMutex * new_mutex = new PlatformMutex;
+
+    core_util_critical_section_enter();
+    if (NULL == mutex) {
+        mutex = new_mutex;
+    }
+    core_util_critical_section_exit();
+
+    if (mutex != new_mutex) {
+        delete new_mutex;
+    }
+    return mutex;
+}
+
+FATFileSystem::FATFileSystem(const char* n) : FileSystemLike(n), _mutex(get_fat_mutex()) {
+    lock();
     debug_if(FFS_DBG, "FATFileSystem(%s)\n", n);
     for(int i=0; i<_VOLUMES; i++) {
         if(_ffs[i] == 0) {
             _ffs[i] = this;
             _fsid[0] = '0' + i;
             _fsid[1] = '\0';
-            debug_if(FFS_DBG, "Mounting [%s] on ffs drive [%s]\n", _name, _fsid);
+            debug_if(FFS_DBG, "Mounting [%s] on ffs drive [%s]\n", getName(), _fsid);
             f_mount(&_fs, _fsid, 0);
+            unlock();
             return;
         }
     }
     error("Couldn't create %s in FATFileSystem::FATFileSystem\n", n);
+    unlock();
 }
 
 FATFileSystem::~FATFileSystem() {
+    lock();
     for (int i=0; i<_VOLUMES; i++) {
         if (_ffs[i] == this) {
             _ffs[i] = 0;
             f_mount(NULL, _fsid, 0);
         }
     }
+    unlock();
 }
 
 FileHandle *FATFileSystem::open(const char* name, int flags) {
-    debug_if(FFS_DBG, "open(%s) on filesystem [%s], drv [%s]\n", name, _name, _fsid);
+    lock();
+    debug_if(FFS_DBG, "open(%s) on filesystem [%s], drv [%s]\n", name, getName(), _fsid);
     char n[64];
     sprintf(n, "%s:/%s", _fsid, name);
 
@@ -92,63 +115,95 @@ FileHandle *FATFileSystem::open(const char* name, int flags) {
     FRESULT res = f_open(&fh, n, openmode);
     if (res) {
         debug_if(FFS_DBG, "f_open('w') failed: %d\n", res);
+        unlock();
         return NULL;
     }
     if (flags & O_APPEND) {
         f_lseek(&fh, fh.fsize);
     }
-    return new FATFileHandle(fh);
+    FATFileHandle * handle = new FATFileHandle(fh, _mutex);
+    unlock();
+    return handle;
 }
 
 int FATFileSystem::remove(const char *filename) {
+    lock();
     FRESULT res = f_unlink(filename);
     if (res) {
         debug_if(FFS_DBG, "f_unlink() failed: %d\n", res);
+        unlock();
         return -1;
     }
+    unlock();
     return 0;
 }
 
 int FATFileSystem::rename(const char *oldname, const char *newname) {
+    lock();
     FRESULT res = f_rename(oldname, newname);
     if (res) {
         debug_if(FFS_DBG, "f_rename() failed: %d\n", res);
+        unlock();
         return -1;
     }
+    unlock();
     return 0;
 }
 
 int FATFileSystem::format() {
+    lock();
     FRESULT res = f_mkfs(_fsid, 0, 512); // Logical drive number, Partitioning rule, Allocation unit size (bytes per cluster)
     if (res) {
         debug_if(FFS_DBG, "f_mkfs() failed: %d\n", res);
+        unlock();
         return -1;
     }
+    unlock();
     return 0;
 }
 
 DirHandle *FATFileSystem::opendir(const char *name) {
+    lock();
     FATFS_DIR dir;
     FRESULT res = f_opendir(&dir, name);
     if (res != 0) {
+        unlock();
         return NULL;
     }
-    return new FATDirHandle(dir);
+    FATDirHandle *handle = new FATDirHandle(dir, _mutex);
+    unlock();
+    return handle;
 }
 
 int FATFileSystem::mkdir(const char *name, mode_t mode) {
+    lock();
     FRESULT res = f_mkdir(name);
+    unlock();
     return res == 0 ? 0 : -1;
 }
 
 int FATFileSystem::mount() {
+    lock();
     FRESULT res = f_mount(&_fs, _fsid, 1);
+    unlock();
     return res == 0 ? 0 : -1;
 }
 
 int FATFileSystem::unmount() {
-    if (disk_sync())
+    lock();
+    if (disk_sync()) {
+        unlock();
         return -1;
+    }
     FRESULT res = f_mount(NULL, _fsid, 0);
+    unlock();
     return res == 0 ? 0 : -1;
 }
+
+void FATFileSystem::lock() {
+    _mutex->lock();
+}
+
+void FATFileSystem::unlock() {
+    _mutex->unlock();
+}