perf, x86: P4 PMU - Drop redundant WARN_ON_ONCE

This WARN_ON_ONCE triggers a false alarm on SMP because nmi-watchdog uses a single global 'wd_hw_attr' variable to serve perf event attributes and once p4_hw_watchdog_set_attr has modified it subsequent calls on the rest cpus trigger the warning.

It is safe to simply drop it since we know the caller may pass already altered type and config.

Repoted-by Steven Rostedt <[email protected]>

Signed-off-by Cyrill Gorcunov <[email protected]>

---
 arch/x86/kernel/cpu/perf_event_p4.c |    3 ---
 1 file changed, 3 deletions(-)

Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c
===================================================================

arch/x86/kernel/cpu/perf_event_p4.c +0 -3

@@ -726,9 +726,6 @@ static void p4_hw_watchdog_set_attr(stru
 	 * that named "non-sleeping" ticks as recommended
 	 * by Intel SDM Vol3b.
 	 */
-	WARN_ON_ONCE(wd_attr->type	!= PERF_TYPE_HARDWARE ||
-		     wd_attr->config	!= PERF_COUNT_HW_CPU_CYCLES);
-
 	wd_attr->type	= PERF_TYPE_RAW;
 	wd_attr->config	=
 		p4_config_pack_escr(P4_ESCR_EVENT(P4_EVENT_EXECUTION_EVENT)		|

Quoted 6 lines · Cyrill Gorcunov

This WARN_ON_ONCE triggers a false alarm on SMP because nmi-watchdog uses a single global 'wd_hw_attr' variable to serve perf event attributes and once p4_hw_watchdog_set_attr has modified it subsequent calls on the rest cpus trigger the warning.

Quoted 4 lines

It is safe to simply drop it since we know the caller may pass already altered type and config.

Repoted-by Steven Rostedt <[email protected]>

Repoted? Hmm, maybe symbolically I put this code in a different pot.

Reported-and-tested-by Steven Rostedt <[email protected]>