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+>Synchronization</TITLE
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+><H1
+><A
+NAME="FILEIO-SYNCHRONIZATION">Chapter 24. Synchronization</H1
+><P
+>The FILEIO infrastructure provides a synchronization mechanism for
+controlling concurrent access to filesystems. This allows existing
+filesystems to be ported to eCos, even if they do not have their own
+synchronization mechanisms. It also allows new filesystems to be
+implemented easily without having to consider the synchronization
+issues.</P
+><P
+>The infrastructure maintains a mutex for each entry in each of
+the main tables: filesystem table, mount table and file table. For
+each class of operation each of these mutexes may be locked before the
+corresponding filesystem operation is invoked.</P
+><P
+>The synchronization protocol required by a filesystem is described
+by the <TT
+CLASS="STRUCTFIELD"
+><I
+>syncmode</I
+></TT
+> field of the filesystem
+table entry. This is a combination of the following flags:</P
+><P
+></P
+><DIV
+CLASS="VARIABLELIST"
+><DL
+><DT
+><TT
+CLASS="LITERAL"
+>CYG_SYNCMODE_FILE_FILESYSTEM</TT
+></DT
+><DD
+><P
+>Lock the filesystem table entry mutex
+during all filesystem level operations.</P
+></DD
+><DT
+><TT
+CLASS="LITERAL"
+>CYG_SYNCMODE_FILE_MOUNTPOINT</TT
+></DT
+><DD
+><P
+>Lock the mount table entry mutex
+during all filesystem level operations.</P
+></DD
+><DT
+><TT
+CLASS="LITERAL"
+>CYG_SYNCMODE_IO_FILE</TT
+></DT
+><DD
+><P
+>Lock the file table entry mutex during all
+I/O operations.</P
+></DD
+><DT
+><TT
+CLASS="LITERAL"
+>CYG_SYNCMODE_IO_FILESYSTEM</TT
+></DT
+><DD
+><P
+>Lock the filesystem table entry mutex during all I/O operations.</P
+></DD
+><DT
+><TT
+CLASS="LITERAL"
+>CYG_SYNCMODE_IO_MOUNTPOINT</TT
+></DT
+><DD
+><P
+>Lock the mount table entry mutex during all I/O operations.</P
+></DD
+><DT
+><TT
+CLASS="LITERAL"
+>CYG_SYNCMODE_SOCK_FILE</TT
+></DT
+><DD
+><P
+>Lock the file table entry mutex during all socket operations.</P
+></DD
+><DT
+><TT
+CLASS="LITERAL"
+>CYG_SYNCMODE_SOCK_NETSTACK</TT
+></DT
+><DD
+><P
+>Lock the network stack table entry mutex during all socket operations.</P
+></DD
+><DT
+><TT
+CLASS="LITERAL"
+>CYG_SYNCMODE_NONE</TT
+></DT
+><DD
+><P
+>Perform no locking at all during any operations.</P
+></DD
+></DL
+></DIV
+><P
+>The value of the <TT
+CLASS="STRUCTFIELD"
+><I
+>syncmode</I
+></TT
+> field in the
+filesystem table entry will be copied by the infrastructure to the
+open file object after a successful <TT
+CLASS="FUNCTION"
+>open()</TT
+> operation.</P
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