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>

1 files changed, 3 insertions, 8 deletions

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 0d2e37c5773..469e9635ff0 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -104,13 +104,6 @@ static inline notrace void set_soft_enabled(unsigned long enable)
 	: : "r" (enable), "i" (offsetof(struct paca_struct, soft_enabled)));
 }
 
-#ifdef CONFIG_PERF_COUNTERS
-notrace void __weak perf_counter_do_pending(void)
-{
-	set_perf_counter_pending(0);
-}
-#endif
-
 notrace void raw_local_irq_restore(unsigned long en)
 {
 	/*
@@ -142,8 +135,10 @@ notrace void raw_local_irq_restore(unsigned long en)
 			iseries_handle_interrupts();
 	}
 
-	if (get_perf_counter_pending())
+	if (get_perf_counter_pending()) {
+		clear_perf_counter_pending();
 		perf_counter_do_pending();
+	}
 
 	/*
 	 * if (get_paca()->hard_enabled) return;