perf_counter: unify and fix delayed counter wakeup

While going over the wakeup code I noticed delayed wakeups only work
for hardware counters but basically all software counters rely on
them.

This patch unifies and generalizes the delayed wakeup to fix this
issue.

Since we're dealing with NMI context bits here, use a cmpxchg() based
single link list implementation to track counters that have pending
wakeups.

[ This should really be generic code for delayed wakeups, but since we
  cannot use cmpxchg()/xchg() in generic code, I've let it live in the
  perf_counter code. -- Eric Dumazet could use it to aggregate the
  network wakeups. ]

Furthermore, the x86 method of using TIF flags was flawed in that its
quite possible to end up setting the bit on the idle task, loosing the
wakeup.

The powerpc method uses per-cpu storage and does appear to be
sufficient.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Orig-LKML-Reference: <20090330171023.153932974@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 0 insertions, 6 deletions

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 611615a92c90..0a813b17b172 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -6,7 +6,6 @@
  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
  *  2000-2002   x86-64 support by Andi Kleen
  */
-#include <linux/perf_counter.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/smp.h>
@@ -872,11 +871,6 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
                 tracehook_notify_resume(regs);
         }
 
-        if (thread_info_flags & _TIF_PERF_COUNTERS) {
-                clear_thread_flag(TIF_PERF_COUNTERS);
-                perf_counter_notify(regs);
-        }
-
 #ifdef CONFIG_X86_32
         clear_thread_flag(TIF_IRET);
 #endif /* CONFIG_X86_32 */