libc/stdio: Add stdio file locking functions

Add flockfile(), ftrylockfile() and funlockfile() functions [1].

[1] POSIX.1-2008 / System Interfaces / flockfile
    https://pubs.opengroup.org/onlinepubs/9699919799.2008edition/functions/flockfile.html

Signed-off-by: Miguel Herranz <miguel@midokura.com>
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

Documentation/reference/user/10_filesystem.rst

@@ -268,6 +268,7 @@ Standard I/O
   int    fgetc(FAR FILE *stream);
   int    fgetpos(FAR FILE *stream, FAR fpos_t *pos);
   FAR char *fgets(FAR char *s, int n, FAR FILE *stream);
+  void   flockfile(FAR FILE *stream);
   FAR FILE *fopen(FAR const char *path, FAR const char *type);
   int    fprintf(FAR FILE *stream, FAR const char *format, ...);
   int    fputc(int c, FAR FILE *stream);
@@ -278,6 +279,8 @@ Standard I/O
   int    fseek(FAR FILE *stream, long int offset, int whence);
   int    fsetpos(FAR FILE *stream, FAR fpos_t *pos);
   long   ftell(FAR FILE *stream);
+  int    ftrylockfile(FAR FILE *stream);
+  void   funlockfile(FAR FILE *stream);
   size_t fwrite(FAR const void *ptr, size_t size, size_t n_items, FAR FILE *stream);
   FAR char *gets(FAR char *s);
   FAR char *gets_s(FAR char *s, rsize_t n);

fs/vfs/fs_fdopen.c

@@ -194,7 +194,7 @@ int fs_fdopen(int fd, int oflags, FAR struct tcb_s *tcb,
 
       /* Initialize the mutex the manages access to the buffer */
 
-      lib_lock_init(stream);
+      nxrmutex_init(&stream->fs_lock);
     }
   else
     {

include/nuttx/fs/fs.h

@@ -475,9 +475,9 @@ struct filelist
 struct file_struct
 {
   FAR struct file_struct *fs_next;      /* Pointer to next file stream */
+  rmutex_t                fs_lock;      /* Recursive lock */
   int                     fs_fd;        /* File descriptor associated with stream */
 #ifndef CONFIG_STDIO_DISABLE_BUFFERING
-  rmutex_t                fs_lock;      /* Recursive lock */
   FAR unsigned char      *fs_bufstart;  /* Pointer to start of buffer */
   FAR unsigned char      *fs_bufend;    /* Pointer to 1 past end of buffer */
   FAR unsigned char      *fs_bufpos;    /* Current position in buffer */

include/nuttx/lib/lib.h

@@ -109,18 +109,6 @@ void lib_stream_initialize(FAR struct task_group_s *group);
 void lib_stream_release(FAR struct task_group_s *group);
 #endif
 
-/* Functions defined in lib_filesem.c ***************************************/
-
-#ifdef CONFIG_STDIO_DISABLE_BUFFERING
-#  define lib_lock_init(s)
-#  define lib_take_lock(s)
-#  define lib_give_lock(s)
-#else
-void lib_lock_init(FAR struct file_struct *stream);
-void lib_take_lock(FAR struct file_struct *stream);
-void lib_give_lock(FAR struct file_struct *stream);
-#endif
-
 /* Functions defined in lib_srand.c *****************************************/
 
 unsigned long nrand(unsigned long limit);

include/stdio.h

@@ -173,6 +173,10 @@ int    setvbuf(FAR FILE *stream, FAR char *buffer, int mode, size_t size);
 
 int    ungetc(int c, FAR FILE *stream);
 
+void flockfile(FAR FILE *stream);
+int ftrylockfile(FAR FILE *stream);
+void funlockfile(FAR FILE *stream);
+
 /* Operations on the stdout stream, buffers, paths,
  * and the whole printf-family
  */

libs/libc/libc.csv

@@ -53,6 +53,7 @@
 "fgetpos","stdio.h","defined(CONFIG_FILE_STREAM)","int","FAR FILE *","FAR fpos_t *"
 "fgets","stdio.h","defined(CONFIG_FILE_STREAM)","FAR char *","FAR char *","int","FAR FILE *"
 "fileno","stdio.h","","int","FAR FILE *"
+"flockfile","stdio.h","!defined(CONFIG_FILE_STREAM)","void","FAR FILE *"
 "fnmatch","fnmatch.h","","int","FAR const char *","FAR const char *","int"
 "fopen","stdio.h","defined(CONFIG_FILE_STREAM)","FAR FILE *","FAR const char *","FAR const char *"
 "fprintf","stdio.h","defined(CONFIG_FILE_STREAM)","int","FAR FILE *","FAR const IPTR char *","..."
@@ -65,6 +66,8 @@
 "fsetpos","stdio.h","defined(CONFIG_FILE_STREAM)","int","FAR FILE *","FAR fpos_t *"
 "fstatvfs","sys/statvfs.h","","int","int","FAR struct statvfs *"
 "ftell","stdio.h","defined(CONFIG_FILE_STREAM)","long","FAR FILE *"
+"ftrylockfile","stdio.h","!defined(CONFIG_FILE_STREAM)","int","FAR FILE *"
+"funlockfile","stdio.h","!defined(CONFIG_FILE_STREAM)","void","FAR FILE *"
 "fwrite","stdio.h","defined(CONFIG_FILE_STREAM)","size_t","FAR const void *","size_t","size_t","FAR FILE *"
 "gai_strerror","netdb.h","defined(CONFIG_LIBC_NETDB)","FAR const char *","int"
 "getaddrinfo","netdb.h","defined(CONFIG_LIBC_NETDB)","int","FAR const char *","FAR const char *","FAR const struct addrinfo *","FAR struct addrinfo **"

libs/libc/stdio/Make.defs

@@ -44,7 +44,7 @@ CSRCS += lib_rdflush.c lib_wrflush.c lib_putc.c lib_fputc.c
 CSRCS += lib_fputs.c lib_ungetc.c lib_fprintf.c lib_vfprintf.c
 CSRCS += lib_feof.c lib_ferror.c lib_rewind.c lib_clearerr.c
 CSRCS += lib_scanf.c lib_vscanf.c lib_fscanf.c lib_vfscanf.c lib_tmpfile.c
-CSRCS += lib_setbuf.c lib_setvbuf.c lib_libstream.c lib_libfilesem.c
+CSRCS += lib_setbuf.c lib_setvbuf.c lib_libstream.c lib_libfilelock.c
 endif
 
 # Add the stdio directory to the build

libs/libc/stdio/lib_ftello.c

@@ -53,7 +53,7 @@
 static off_t lib_getoffset(FAR FILE *stream)
 {
   off_t offset = 0;
-  lib_take_lock(stream);
+  flockfile(stream);
 
   if (stream->fs_bufstart !=
       NULL && stream->fs_bufread !=
@@ -71,7 +71,7 @@ static off_t lib_getoffset(FAR FILE *stream)
       offset = -(stream->fs_bufpos - stream->fs_bufstart);
     }
 
-  lib_give_lock(stream);
+  funlockfile(stream);
   return offset;
 }
 #else

libs/libc/stdio/lib_libfflush.c

@@ -73,7 +73,7 @@ ssize_t lib_fflush(FAR FILE *stream, bool bforce)
 
   /* Make sure that we have exclusive access to the stream */
 
-  lib_take_lock(stream);
+  flockfile(stream);
 
   /* Check if there is an allocated I/O buffer */
 
@@ -156,11 +156,11 @@ ssize_t lib_fflush(FAR FILE *stream, bool bforce)
    * remaining in the buffer.
    */
 
-  lib_give_lock(stream);
+  funlockfile(stream);
   return stream->fs_bufpos - stream->fs_bufstart;
 
 errout_with_lock:
-  lib_give_lock(stream);
+  funlockfile(stream);
   return ret;
 
 #else

libs/libc/stdio/lib_libfilelock.c

@@ -1,5 +1,5 @@
 /****************************************************************************
- * libs/libc/stdio/lib_libfilesem.c
+ * libs/libc/stdio/lib_libfilelock.c
  *
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
@@ -29,46 +29,36 @@
 #include <errno.h>
 #include <assert.h>
 
-#include <nuttx/semaphore.h>
+#include <nuttx/mutex.h>
 #include <nuttx/fs/fs.h>
 
-#include "libc.h"
-
-#ifndef CONFIG_STDIO_DISABLE_BUFFERING
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
 
 /****************************************************************************
- * lib_lock_init
+ * flockfile
  ****************************************************************************/
 
-void lib_lock_init(FAR struct file_struct *stream)
+void flockfile(FAR struct file_struct *stream)
-{
-  /* Initialize the LIB mutex to one (to support one-at-a-time access
-   * to private data sets.
-   */
-
-  nxrmutex_init(&stream->fs_lock);
-}
-
-/****************************************************************************
- * lib_take_lock
- ****************************************************************************/
-
-void lib_take_lock(FAR struct file_struct *stream)
 {
   nxrmutex_lock(&stream->fs_lock);
 }
 
 /****************************************************************************
- * lib_give_lock
+ * flockfile
  ****************************************************************************/
 
-void lib_give_lock(FAR struct file_struct *stream)
+int ftrylockfile(FAR struct file_struct *stream)
+{
+  return nxrmutex_trylock(&stream->fs_lock);
+}
+
+/****************************************************************************
+ * funlockfile
+ ****************************************************************************/
+
+void funlockfile(FAR struct file_struct *stream)
 {
   nxrmutex_unlock(&stream->fs_lock);
 }
-
-#endif /* CONFIG_STDIO_DISABLE_BUFFERING */

libs/libc/stdio/lib_libfread.c

@@ -70,7 +70,7 @@ ssize_t lib_fread(FAR void *ptr, size_t count, FAR FILE *stream)
     {
       /* The stream must be stable until we complete the read */
 
-      lib_take_lock(stream);
+      flockfile(stream);
 
 #if CONFIG_NUNGET_CHARS > 0
       /* First, re-read any previously ungotten characters */
@@ -304,7 +304,7 @@ shortread:
           stream->fs_flags |= __FS_FLAG_EOF;
         }
 
-      lib_give_lock(stream);
+      funlockfile(stream);
       return count - remaining;
     }
 
@@ -312,6 +312,6 @@ shortread:
 
 errout_with_errno:
   stream->fs_flags |= __FS_FLAG_ERROR;
-  lib_give_lock(stream);
+  funlockfile(stream);
   return ERROR;
 }

libs/libc/stdio/lib_libfwrite.c

@@ -83,7 +83,7 @@ ssize_t lib_fwrite(FAR const void *ptr, size_t count, FAR FILE *stream)
 
   /* Get exclusive access to the stream */
 
-  lib_take_lock(stream);
+  flockfile(stream);
 
   /* If the buffer is currently being used for read access, then
    * discard all of the read-ahead data.  We do not support concurrent
@@ -157,7 +157,7 @@ ssize_t lib_fwrite(FAR const void *ptr, size_t count, FAR FILE *stream)
   ret = (uintptr_t)src - (uintptr_t)start;
 
 errout_with_lock:
-  lib_give_lock(stream);
+  funlockfile(stream);
 
 errout:
   if (ret < 0)

libs/libc/stdio/lib_libstream.c

@@ -30,7 +30,7 @@
 #include <errno.h>
 
 #include <nuttx/kmalloc.h>
-#include <nuttx/semaphore.h>
+#include <nuttx/mutex.h>
 #include <nuttx/sched.h>
 #include <nuttx/fs/fs.h>
 #include <nuttx/lib/lib.h>
@@ -73,11 +73,11 @@ void lib_stream_initialize(FAR struct task_group_s *group)
   /* Initialize stdin, stdout and stderr stream */
 
   list->sl_std[0].fs_fd = -1;
-  lib_lock_init(&list->sl_std[0]);
+  nxrmutex_init(&list->sl_std[0].fs_lock);
   list->sl_std[1].fs_fd = -1;
-  lib_lock_init(&list->sl_std[1]);
+  nxrmutex_init(&list->sl_std[1].fs_lock);
   list->sl_std[2].fs_fd = -1;
-  lib_lock_init(&list->sl_std[2]);
+  nxrmutex_init(&list->sl_std[2].fs_lock);
 }
 
 /****************************************************************************

libs/libc/stdio/lib_puts.c

@@ -50,7 +50,7 @@ int puts(FAR const IPTR char *s)
 
   /* Write the string (the next two steps must be atomic) */
 
-  lib_take_lock(stream);
+  flockfile(stream);
 
   /* Write the string without its trailing '\0' */
 
@@ -80,7 +80,7 @@ int puts(FAR const IPTR char *s)
         }
     }
 
-  lib_give_lock(stdout);
+  funlockfile(stdout);
   return nput;
 #else
   size_t len = strlen(s);

libs/libc/stdio/lib_rdflush.c

@@ -65,7 +65,7 @@ int lib_rdflush(FAR FILE *stream)
 
   /* Get exclusive access to the stream */
 
-  lib_take_lock(stream);
+  flockfile(stream);
 
   /* If the buffer is currently being used for read access, then discard all
    * of the read-ahead data. We do not support concurrent buffered read/write
@@ -98,12 +98,12 @@ int lib_rdflush(FAR FILE *stream)
 
       if (fseek(stream, -rdoffset, SEEK_CUR) < 0)
         {
-          lib_give_lock(stream);
+          funlockfile(stream);
           return ERROR;
         }
     }
 
-  lib_give_lock(stream);
+  funlockfile(stream);
   return OK;
 }
 

libs/libc/stdio/lib_rewind.c

@@ -46,8 +46,8 @@ void rewind(FAR FILE *stream)
       return;
     }
 
-  lib_take_lock(stream);
+  flockfile(stream);
-  (void) fseek(stream, 0L, SEEK_SET);
+  fseek(stream, 0L, SEEK_SET);
   stream->fs_flags &= ~__FS_FLAG_ERROR;
-  lib_give_lock(stream);
+  funlockfile(stream);
 }

libs/libc/stdio/lib_setvbuf.c

@@ -125,7 +125,7 @@ int setvbuf(FAR FILE *stream, FAR char *buffer, int mode, size_t size)
 
   /* Make sure that we have exclusive access to the stream */
 
-  lib_take_lock(stream);
+  flockfile(stream);
 
   /* setvbuf() may only be called AFTER the stream has been opened and
    * BEFORE any operations have been performed on the stream.
@@ -246,11 +246,11 @@ int setvbuf(FAR FILE *stream, FAR char *buffer, int mode, size_t size)
 
 reuse_buffer:
   stream->fs_flags    = flags;
-  lib_give_lock(stream);
+  funlockfile(stream);
   return OK;
 
 errout_with_lock:
-  lib_give_lock(stream);
+  funlockfile(stream);
 
 errout:
   set_errno(errcode);

libs/libc/stdio/lib_vfprintf.c

@@ -48,9 +48,9 @@ int vfprintf(FAR FILE *stream, FAR const IPTR char *fmt, va_list ap)
    * before being pre-empted by the next thread.
    */
 
-  lib_take_lock(stream);
+  flockfile(stream);
   n = lib_vsprintf(&stdoutstream.public, fmt, ap);
-  lib_give_lock(stream);
+  funlockfile(stream);
 
   return n;
 }

libs/libc/stdio/lib_vfscanf.c

@@ -55,7 +55,7 @@ int vfscanf(FAR FILE *stream, FAR const IPTR char *fmt, va_list ap)
        * by the next thread.
        */
 
-      lib_take_lock(stream);
+      flockfile(stream);
 
       n = lib_vscanf(&stdinstream.public, &lastc, fmt, ap);
 
@@ -68,7 +68,7 @@ int vfscanf(FAR FILE *stream, FAR const IPTR char *fmt, va_list ap)
           ungetc(lastc, stream);
         }
 
-      lib_give_lock(stream);
+      funlockfile(stream);
     }
 
   return n;