On Tue, 8 May 2001, John Baldwin wrote:

> That's easy enough.  Well, it used to be at least.  You can use 'ps' to
> find the address of the struct proc (first pointer in the display) and
> then do 'call psignal(addr, 9)' to send SIGKILL to the process.  Then
> hit 'c' to continue and voila, the process dies.  I think that may panic
> now due to proc lock not being held (though the debugger shouldn't need
> any locks in theory.) Perhaps mtx_assert() should honor db_active and
> not panic if it is set. 

I followed everything here fine until you asserted that the debugger
shouldn't need any locks.  I guess I don't see why that is, at least in
terms of not corrupting structures.  From a practical perspective, the
debugger is like any other interupt-driven preemptive code-path: if you
want to modify a structure, you need to synchronize appropriately to avoid
corrupting the structure.  This may not be something you really want to do
in a debugger, so in that sense perhaps you *shouldn't* grab a lock in the
debugger, but to perform the described action safely, you *should* grab a
lock so as not to corrupt fields of the proc structure (i.e., if you broke
into the debugger during a non-atomic flags update).  Violating system
invariants is something you should be allowed to do in a debugger, but
this sounded like it was a feature people were looking from to recover
from unhappy behavior, not to introduce it :-).

Robert N M Watson             FreeBSD Core Team, TrustedBSD Project
[EMAIL PROTECTED]      NAI Labs, Safeport Network Services

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