state of the currently running thread and restores the state of the
thread we're switching to.
-Using the @command{gdb} debugger, slowly trace through a context
-switch to see what happens (@pxref{gdb}). You can set a
+Using the GDB debugger, slowly trace through a context
+switch to see what happens (@pxref{GDB}). You can set a
breakpoint on @func{schedule} to start out, and then
-single-step from there.@footnote{@command{gdb} might tell you that
-@func{schedule} doesn't exist, which is arguably a @command{gdb} bug.
+single-step from there.@footnote{GDB might tell you that
+@func{schedule} doesn't exist, which is arguably a 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}.} Be sure
interrupt handling latency, which can make a machine feel sluggish if
taken too far.
-You may need to add or modify code where interrupts are already
-disabled, such as in @func{sema_up} or @func{sema_down}. You should
-still try to keep this code as short as you can.
+The synchronization primitives themselves in @file{synch.c} are
+implemented by disabling interrupts. You may need to increase the
+amount of code that runs with interrupts disabled here, but you should
+still try to keep it to a minimum.
Disabling interrupts can be useful for debugging, if you want to make
sure that a section of code is not interrupted. You should remove