svn commit: r218967 - head/sys/kern
Alexander Best
arundel at freebsd.org
Wed Feb 23 14:30:13 UTC 2011
On Wed Feb 23 11, Kostik Belousov wrote:
> On Wed, Feb 23, 2011 at 01:57:34PM +0000, Alexander Best wrote:
> > On Wed Feb 23 11, Kostik Belousov wrote:
> > > On Wed, Feb 23, 2011 at 12:56:25PM +0000, John Baldwin wrote:
> > > > Author: jhb
> > > > Date: Wed Feb 23 12:56:25 2011
> > > > New Revision: 218967
> > > > URL: http://svn.freebsd.org/changeset/base/218967
> > > >
> > > > Log:
> > > > Fix off-by-one error in check against max_threads_per_proc.
> > > >
> > > > Submitted by: arundel
> > > > MFC after: 1 week
> > > >
> > > > Modified:
> > > > head/sys/kern/kern_thr.c
> > > >
> > > > Modified: head/sys/kern/kern_thr.c
> > > > ==============================================================================
> > > > --- head/sys/kern/kern_thr.c Wed Feb 23 10:28:37 2011 (r218966)
> > > > +++ head/sys/kern/kern_thr.c Wed Feb 23 12:56:25 2011 (r218967)
> > > > @@ -153,7 +153,7 @@ create_thread(struct thread *td, mcontex
> > > > p = td->td_proc;
> > > >
> > > > /* Have race condition but it is cheap. */
> > > > - if (p->p_numthreads >= max_threads_per_proc) {
> > > > + if (p->p_numthreads > max_threads_per_proc) {
> > > > ++max_threads_hits;
> > > > return (EPROCLIM);
> > > > }
> > >
> > > I do not think there was off by one error. The create_thread() function
> > > is called to create new thread, and before the process thread counter
> > > is incremented in thread_link(). The old test tried to not allow more
> > > then max_threads_per_proc threads in a process, now it allows to
> > > create max_threads_per_proc.
> >
> > doesn't the semantics of the term "maximum" imply that it's own value is also
> > valid?
> >
> > if a sign says maximum weight 2000kg, does that mean that a weight of 2000kg is
> > invalid and the highest valid weight is 1999,999..kg?
> >
> > cheers.
> > alex
> >
> > >
> > > My guess is that the reference to mentioned pthread_vfork_test failed
> > > because reporter set kern.threads.max_threads_per_proc to 100. The
> > > test actually tries to create 101 threads, 1 main + 100 new.
> >
> > so the main process counts as 1 thread and for each pthread_create
> > invokation the thread number gets bumped up?
> >
> > so with a process doing a single pthread_create() that would imply
> > this process is having a thread count of 2?
>
> Exactly. The main thread is the same as all others (almost).
thanks for the hint. i wasn't aware of that. however now proctsta -akk also
displaying a thread id for a process with no additional threads makes a lot
more sense. ;)
so in theory:
kern.threads.max_threads_per_proc=0 and kern.threads.max_threads_per_proc=1
both forbid a process to trigger any new threads.
cheers.
alex
--
a13x
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