In systemtap, we've changed to stopping a thread before setting up the
events we're interested in (besides quiesce/death). So, basically, it
looks like this (without much error handling):
// initial attach logic
// ... find an interesting thread ...
ops.report_quiesce = quiesce_handler;
ops.report_syscall_entry = syscall_entry_handler;
engine = utrace_attach_task(tsk, UTRACE_ATTACH_CREATE, &ops, data);
rc = utrace_set_events(tsk, engine,
(UTRACE_EVENT(DEATH) | UTRACE_STOP | UTRACE_EVENT(QUIESCE)));
// ... do other stuff ...
// quiesce handler
u32
quiesce_handler(enum utrace_resume_action action,
struct utrace_attached_engine *engine,
struct task_struct *tsk,
unsigned long event)
{
int rc;
// Turn off quiesce handling and turn on syscall handling
rc = utrace_set_events(tsk, engine,
UTRACE_EVENT(DEATH) | UTRACE_EVENT(SYSCALL_ENTRY));
if (rc == -EINPROGRESS) {
rc = utrace_barrier(tsk, engine);
if (rc != 0)
printk(KERN_ERR
"utrace_barrier returned error %d on pid %d",
rc, (int)tsk->pid);
rc = utrace_set_events(tsk, engine,
UTRACE_EVENT(DEATH) | UTRACE_EVENT(SYSCALL_ENTRY));
}
if (rc != 0)
printk(KERN_ERR
"utrace_set_events returned error %d on pid %d",
rc, (int)tsk->pid);
// ... do other stuff ...
return UTRACE_RESUME;
}
The utrace_barrier() call always returns 0, but the utrace_set_events()
calls always return -EINPRPOGRESS. I've put the -EINPROGRESS logic in a
loop, but even after 10 iterations utrace_set_events() never succeeds.
This is on 2.6.27-0.287.rc4.git7.fc10.x86_64.
So, am I doing this incorrectly? Or is there a bug here in utrace
(where it doesn't expect to see a utrace_set_events() from within a
handler on the same thread)? If I'm doing this incorrectly, I'd like
help in figuring out what I should be doing.
(In the original utrace there was UTRACE_ACTION_NEWSTATE which allowed
you to change the flags from the handler, but I haven't seen anything
similar in the current utrace.)
Thanks for the help.
--
David Smith
[EMAIL PROTECTED]
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)
