SMP races in proc with thread_struct

Perhaps this is old news...but... I can easily create a race when reading /proc//stat (fs/proc/{base.c,array.c}) where a rapidly reading application, such as "top", starts reading stats for a thread which goes away during the read. This is easily reproduced with a program that rapidly forks and

Re: SMP races in proc with thread_struct

Alexander Viro wrote: > > On Tue, 1 May 2001, Todd Inglett wrote: > > > Perhaps this is old news...but... > > > > I can easily create a race when reading /proc//stat > > (fs/proc/{base.c,array.c}) where a rapidly reading application, such as > > "t

Re: SMP races in proc with thread_struct

Ok, I've got this isolated. Here's the sequence of events: 1. Some process T (probably "top") opens /proc/N/stat. 2. While holding tasklist_lock the proc code does a get_task_struct() to add a ref count to the page. 3. Process N exits. 4. The parent of process N exits. 5. Process T reads fr

Re: SMP races in proc with thread_struct

Andreas Ferber wrote: > > On Fri, May 04, 2001 at 10:46:43PM +1000, Keith Owens wrote: > > > For a read only case, the only important > > thing is not to die, one occurrence of bad data is tolerable. > > Strong NACK. The pages where the bad data comes from may in some cases > already be reclaim