Explain why `break schedule' might not work and offer workarounds.

diff --git a/doc/threads.texi b/doc/threads.texi
index 63aed6928bb287218bc9d7ce9a8458d924837e0e..f219db44fd800b94370d6ad2a978aa36f60517b7 100644 (file)
--- a/doc/threads.texi
+++ b/doc/threads.texi
@@ -73,15 +73,21 @@ thread we're switching to.
 Using the @command{gdb} debugger, slowly trace through a context
 switch to see what happens (@pxref{i386-elf-gdb}).  You can set a
 breakpoint on the @func{schedule} function to start out, and then
-single-step from there.  Be sure to keep track of each thread's
-address and state, and what procedures are on the call stack for each
-thread.  You will notice that when one thread calls
-@func{switch_threads}, another thread starts running, and the first
-thing the new thread does is to return from
-@func{switch_threads}.  We realize this comment will seem cryptic to
-you at this point, but you will understand threads once you understand
-why the @func{switch_threads} that gets called is different from the
-@func{switch_threads} that returns.
+single-step from there.@footnote{@command{gdb} might tell you that
+@func{schedule} doesn't exist, which is arguably a @command{gdb} bug.
+You can work around this by setting the breakpoint by filename and
+line number, e.g.@: @code{break thread.c:@var{ln}} where @var{ln} is
+the line number of the first declaration in @func{schedule}.
+Alternatively you can recompile with optimization turned off, by
+removing @samp{-O3} from the @code{CFLAGS} line in
+@file{Make.config}.}  Be sure to keep track of each thread's address
+and state, and what procedures are on the call stack for each thread.
+You will notice that when one thread calls @func{switch_threads},
+another thread starts running, and the first thing the new thread does
+is to return from @func{switch_threads}.  We realize this comment will
+seem cryptic to you at this point, but you will understand threads
+once you understand why the @func{switch_threads} that gets called is
+different from the @func{switch_threads} that returns.
 
 @strong{Warning}: In Pintos, each thread is assigned a small,
 fixed-size execution stack just under @w{4 kB} in size.  The kernel