timers: fix itimer/many thread hang, v2

This is the second resubmission of the posix timer rework patch, posted
a few days ago.

This includes the changes from the previous resubmittion, which addressed
Oleg Nesterov's comments, removing the RCU stuff from the patch and
un-inlining the thread_group_cputime() function for SMP.

In addition, per Ingo Molnar it simplifies the UP code, consolidating much
of it with the SMP version and depending on lower-level SMP/UP handling to
take care of the differences.

It also cleans up some UP compile errors, moves the scheduler stats-related
macros into kernel/sched_stats.h, cleans up a merge error in
kernel/fork.c and has a few other minor fixes and cleanups as suggested
by Oleg and Ingo. Thanks for the review, guys.

Signed-off-by: Frank Mayhar <fmayhar@google.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 4 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 1181b9aac48e..021ae012cc75 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -791,7 +791,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
         int ret;
 
         if (clone_flags & CLONE_THREAD) {
-                ret = thread_group_cputime_clone_thread(current, tsk);
+                ret = thread_group_cputime_clone_thread(current);
                 if (likely(!ret)) {
                         atomic_inc(&current->signal->count);
                         atomic_inc(&current->signal->live);
@@ -834,9 +834,6 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
         task_io_accounting_init(&sig->ioac);
-        INIT_LIST_HEAD(&sig->cpu_timers[0]);
-        INIT_LIST_HEAD(&sig->cpu_timers[1]);
-        INIT_LIST_HEAD(&sig->cpu_timers[2]);
         taskstats_tgid_init(sig);
 
         task_lock(current->group_leader);