On Wednesday, 3 October 2001 at 12:12:14 -0700, Julian Elischer wrote: > I suppose it must have been Peter Penchev who wrote: >> On Wednesday, October 03, 2001 6:14 AM, Greg Lehey <[EMAIL PROTECTED]> wrote: >>> On Tuesday, 2 October 2001 at 12:43:54 -0700, Julian Elischer wrote: >>>> On Tue, 2 Oct 2001, Peter Pentchev wrote: >>>>> On Mon, Oct 01, 2001 at 10:56:24AM +0930, Greg Lehey wrote: >>>>>> [Format recovered--see http://www.lemis.com/email/email-format.html] >>>>>> >>>>>> On Friday, 28 September 2001 at 10:12:14 -0700, Julian Elischer wrote: >>>>>>> On Fri, 28 Sep 2001, Gersh wrote: >>>>>>>> On Fri, 28 Sep 2001, Bernd Walter wrote: >>>>>>>>> On Fri, Sep 28, 2001 at 07:03:51PM +0530, Anjali Kulkarni wrote: >>>>>>>>>> Does anyone know whether it is advisable or not to use >>>>>>>>>> setjmp/longjmp within kernel code? I could not see any >>>>>>>>>> setjmp/longjmp in kernel source code. Is there a good reason for >>>>>>>>>> this or can it be used? >>>>>>>>> >>>>>>>>> You need to look again, it's used in several places in the kernel. >>>>>>>> >>>>>>>> Look at sys/i386/i386/db_interface.c >>>>>>> >>>>>>> Yeah but it would probably be a pretty bad idea to use it without >>>>>>> very careful thought. Especialy with the kernel becoming >>>>>>> pre-emptable in the future.. >>>>>> >>>>>> Can you think of a scenario where it wouldn't work? Preemption >>>>>> doesn't tear stacks apart, right? >>>>> >>>>> How about a case of a longjmp() back from under an acquired lock/mutex? >>>>> Like function A sets up a jump buffer, calls function B, B acquires >>>>> a lock, B calls C, C longjmp()'s back to A; what happens to the lock? >>>>> >>>>> It would work if A were aware of B's lock and the possibility of a code >>>>> path that would end up with it still being held; I presume that this is >>>>> what Julian meant by 'very careful thought'. >>>> >>>> pretty much... >>> >>> That's wrong, of course, but I don't see what this has to do with >>> preemptive kernels. This is the same incorrect usages as performing >>> malloc() and then longjmp()ing over the free(). >> >> Right, that was my question too, doesent seem connected with pre-emptive >> kernels... > > basically it's just that pre-emtion just muddies the waters more..
Or statements which aren't backed up with examples? Greg -- See complete headers for address and phone numbers To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
