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/read.2 b/lib/libc/sys/read.2
index b94341a..ea428fd 100644
--- a/lib/libc/sys/read.2
+++ b/lib/libc/sys/read.2
@@ -107,6 +107,53 @@ The system guarantees to read the number of bytes requested if
 the descriptor references a normal file that has that many bytes left
 before the end-of-file, but in no other case.
 .Pp
+.Sh IMPLEMENTATION NOTES
+.Pp
+In the non-threaded library
+.Fn read
+is implemented as the
+.Va read
+syscall.
+.Pp
+In the threaded library, the
+.Va read
+syscall is assembled to
+.Fn _thread_sys_read
+and
+.Fn read
+is implemented as a function which locks
+.Va d
+for read, then calls
+.Fn _thread_sys_read .
+If the call to
+.Fn _thread_sys_read
+would block, a context switch is performed. Before returning,
+.Fn read
+unlocks
+.Va d .
+.Pp
+In the non-threaded library
+.Fn readv
+is implemented as the
+.Va readv
+syscall.
+.Pp
+In the threaded library, the
+.Va readv
+syscall is assembled to
+.Fn _thread_sys_readv
+and
+.Fn readv
+is implemented as a function which locks
+.Va d
+for read, then calls
+.Fn _thread_sys_readv .
+If the call to
+.Fn _thread_sys_readv
+would block, a context switch is performed. Before returning,
+.Fn readv
+unlocks
+.Va d .
 .Sh RETURN VALUES
 If successful, the
 number of bytes actually read is returned. Upon reading end-of-file,