Hi,
The patch below appears to fix a problem where a number of dead processes
linger on the system. On a highly loaded system, dozens of processes
were found stuck in do_exit(), calling thier very last schedule(), and
then being lost forever.
Processes that are PF_DEAD are cleaned up *after* the context switch,
in a routine called finish_task_switch(task_t *prev). The "prev" gets
the value returned by _switch() in entry.S, but this value comes from
__switch_to (struct task_struct *prev,
struct task_struct *new)
{
old_thread = ¤t->thread; ///XXX shouldn't this be prev, not current?
last = _switch(old_thread, new_thread);
return last;
}
The way I see it, "prev" and "current" are almost always going to be
pointing at the same thing; however, if a "need resched" happens,
or there's a pre-emept or some-such, then prev and current won't be
the same; in which case, finish_task_switch() will end up cleaning
up the old current, instead of prev. This will result in dead processes
hanging around, which will never be scheduled again, and will never
get a chance to have put_task_struct() called on them.
This patch fixes this.
Signed-off-by: Linas Vepstas <[email protected]>
--- arch/ppc64/kernel/process.c.orig 2005-04-18 14:26:42.000000000 -0500
+++ arch/ppc64/kernel/process.c 2005-04-18 14:27:54.000000000 -0500
@@ -204,7 +204,7 @@ struct task_struct *__switch_to(struct t
flush_tlb_pending();
new_thread = &new->thread;
- old_thread = ¤t->thread;
+ old_thread = &prev->thread;
local_irq_save(flags);
last = _switch(old_thread, new_thread);
-
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