perf_counter: abstract wakeup flag setting in core to fix powerpc build
Impact: build fix for powerpc
Commit bd753921015e7905 ("perf_counter: software counter event
infrastructure") introduced a use of TIF_PERF_COUNTERS into the core
perfcounter code. This breaks the build on powerpc because we use
a flag in a per-cpu area to signal wakeups on powerpc rather than
a thread_info flag, because the thread_info flags have to be
manipulated with atomic operations and are thus slower than per-cpu
flags.
This fixes the by changing the core to use an abstracted
set_perf_counter_pending() function, which is defined on x86 to set
the TIF_PERF_COUNTERS flag and on powerpc to set the per-cpu flag
(paca->perf_counter_pending). It changes the previous powerpc
definition of set_perf_counter_pending to not take an argument and
adds a clear_perf_counter_pending, so as to simplify the definition
on x86.
On x86, set_perf_counter_pending() is defined as a macro. Defining
it as a static inline in arch/x86/include/asm/perf_counters.h causes
compile failures because <asm/perf_counters.h> gets included early in
<linux/sched.h>, and the definitions of set_tsk_thread_flag etc. are
therefore not available in <asm/perf_counters.h>. (On powerpc this
problem is avoided by defining set_perf_counter_pending etc. in
<asm/hw_irq.h>.)
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 0018c5e..b39456a 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1433,7 +1433,7 @@
if (nmi) {
counter->wakeup_pending = 1;
- set_tsk_thread_flag(current, TIF_PERF_COUNTERS);
+ set_perf_counter_pending();
} else
wake_up(&counter->waitq);
}