Reviewed by: julian and (hsu?)

Submitted by:	 John Birrel(L?)

changes for threadsafe operations

1 files changed, 47 insertions, 0 deletions

diff --git a/lib/libc/sys/write.2 b/lib/libc/sys/write.2
index de2d3ae..a1e4a51 100644
--- a/lib/libc/sys/write.2
+++ b/lib/libc/sys/write.2
@@ -115,6 +115,53 @@ and
 may write fewer bytes than requested;
 the return value must be noted,
 and the remainder of the operation should be retried when possible.
+.Sh IMPLEMENTATION NOTES
+.Pp
+In the non-threaded library
+.Fn write
+is implemented as the
+.Va write
+syscall.
+.Pp
+In the threaded library, the
+.Va write
+syscall is assembled to
+.Fn _thread_sys_write
+and
+.Fn write
+is implemented as a function which locks
+.Va d
+for read and write, then calls
+.Fn _thread_sys_write .
+If the call to
+.Fn _thread_sys_write
+would block, a context switch is performed. Before returning,
+.Fn write
+unlocks
+.Va d .
+.Pp
+In the non-threaded library
+.Fn writev
+is implemented as the
+.Va writev
+syscall.
+.Pp
+In the threaded library, the
+.Va writev
+syscall is assembled to
+.Fn _thread_sys_writev
+and
+.Fn writev
+is implemented as a function which locks
+.Va d
+for read and write, then calls
+.Fn _thread_sys_writev .
+If the call to
+.Fn _thread_sys_writev
+would block, a context switch is performed. Before returning,
+.Fn writev
+unlocks
+.Va d .
 .Sh RETURN VALUES
 Upon successful completion the number of bytes which were written
 is returned.  Otherwise a -1 is returned and the global variable