ilo-pona/xv6-65oo2
1
0
Fork 0
Code Issues Pull requests Packages Projects Releases Activity

some XXX questions

Browse source
This commit is contained in:
Robert Morris 2019-08-02 14:51:04 -04:00
parent e788af9b81
commit 3bee885ed7
1 changed files with 23 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

27
labs/syscall.html
View file

@ -231,13 +231,15 @@ alarmtest starting
<p>To get started, the best strategy is to first pass test0, which <p>To get started, the best strategy is to first pass test0, which
will force you to handle the main challenge above. Here are some will force you to handle the main challenge above. Here are some
hints how to pass test0: hints how to pass test0:
<p><b>XXX alarm() needs to be defined somewhere.</b><br>
<ul> <ul>
<li>You'll need to modify the Makefile to cause <tt>alarmtest.c</tt> <li>You'll need to modify the Makefile to cause <tt>alarmtest.c</tt>
to be compiled as an xv6 user program. to be compiled as an xv6 user program.
<li>The right declarations to put in <tt>user/user.h</tt> is: <li>The right declaration to put in <tt>user/user.h</tt> is:
<pre> <pre>
int sigalarm(int ticks, void (*handler)()); int sigalarm(int ticks, void (*handler)());
</pre> </pre>
@ -249,7 +251,7 @@ to be compiled as an xv6 user program.
<li>Your <tt>sys_sigalarm()</tt> should store the alarm interval and <li>Your <tt>sys_sigalarm()</tt> should store the alarm interval and
the pointer to the handler function in new fields in the <tt>proc</tt> the pointer to the handler function in new fields in the <tt>proc</tt>
structure; see <tt>kernel/proc.h</tt>. structure, defined in <tt>kernel/proc.h</tt>.
<li>You'll need to keep track of how many ticks have passed since the <li>You'll need to keep track of how many ticks have passed since the
last call (or are left until the next call) to a process's alarm last call (or are left until the next call) to a process's alarm
@ -277,12 +279,29 @@ use only one CPU, which you can do by running
make CPUS=1 qemu make CPUS=1 qemu
</pre> </pre>
<li><b>XXX we need to somehow convey what it is they don't
need to do here, i.e. what part is to be left to
the next section.</b>
<li><b>XXX it's not clear how they can tell whether they
are passing test0(), and should proceed to the next section.
do they need to make sure at this point that they see multiple
alarm! printouts? or is it OK if they see one alarm! and
then a crash?</b>
</ul> </ul>
<h3>test1(): resume interrupted code</h3> <h3>test1(): resume interrupted code</h3>
<p>Test0 doesn't tests whether the handler returns correctly to <p><b>XXX it is surprising that test0() appears to work
interrupted instruction in test0. If you didn't get this right, it perfectly, even though something is seriously wrong
with the way periodic() returns. we should recognize
that something odd is happening, maybe ask them to think
about it, and hint or say why they are not done even though
test0() works.</b>
<p>Test0 doesn't test whether the handler returns correctly to
the interrupted instruction. If you didn't get this right, it
is likely that test1 will fail (the program crashes or the program is likely that test1 will fail (the program crashes or the program
goes into an infinite loop). goes into an infinite loop).