(Timers): Explain about timers and quitting.

diff --git a/lispref/os.texi b/lispref/os.texi
index 1defdcdbe57290ac49fd45f20ae2f4f56d4af043..25a925ded6d0a3d5f0829a8c11ef6adc66fe1151 100644 (file)
--- a/lispref/os.texi
+++ b/lispref/os.texi
@@ -1275,8 +1275,8 @@ This function returns @code{t} if @var{year} is a leap year.
 @section Timers for Delayed Execution
 @cindex timer
 
-  You can set up a @dfn{timer} to call a function at a specified future time or
-after a certain length of idleness.
+  You can set up a @dfn{timer} to call a function at a specified
+future time or after a certain length of idleness.
 
   Emacs cannot run timers at any arbitrary point in a Lisp program; it
 can run them only when Emacs could accept output from a subprocess:
@@ -1285,6 +1285,13 @@ namely, while waiting or inside certain primitive functions such as
 timer's execution may be delayed if Emacs is busy.  However, the time of
 execution is very precise if Emacs is idle.
 
+  Emacs binds @code{inhibit-quit} to @code{t} before calling the timer
+function, because quitting out of many timer functions can leave
+things in an inconsistent state.  This is normally unproblematical
+because most timer functions don't do a lot of work.  Indeed, for a
+timer to calls a function that takes substantial time to run is likely
+to be annoying.
+
 @defun run-at-time time repeat function &rest args
 This function arranges to call @var{function} with arguments @var{args}
 at time @var{time}.  The argument @var{function} is a function to call