diff options
Diffstat (limited to 'labs/syscall.html')
| -rw-r--r-- | labs/syscall.html | 27 |
1 files changed, 23 insertions, 4 deletions
diff --git a/labs/syscall.html b/labs/syscall.html index 67f800e..26cb573 100644 --- a/labs/syscall.html +++ b/labs/syscall.html @@ -231,13 +231,15 @@ alarmtest starting <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 hints how to pass test0: + +<p><b>XXX alarm() needs to be defined somewhere.</b><br> <ul> <li>You'll need to modify the Makefile to cause <tt>alarmtest.c</tt> 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> int sigalarm(int ticks, void (*handler)()); </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 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 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 </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> <h3>test1(): resume interrupted code</h3> -<p>Test0 doesn't tests whether the handler returns correctly to - interrupted instruction in test0. If you didn't get this right, it +<p><b>XXX it is surprising that test0() appears to work +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 goes into an infinite loop). |