MIPS, Perf-events: Fix event check in validate_event() [Linux 2.6.38]

This Linux kernel change "MIPS, Perf-events: Fix event check in validate_event()" is included in the Linux 2.6.38 release. This change is authored by Deng-Cheng Zhu <dengcheng.zhu [at] gmail.com> on Fri Jan 21 16:19:19 2011 +0800. The commit for this change in Linux stable tree is c049b6a (patch).

MIPS, Perf-events: Fix event check in validate_event()

Ignore events that are in off/error state or belong to a different PMU.

This patch originates from the following commit for ARM by Will Deacon:

- 65b4711ff513767341aa1915c822de6ec0de65cb
    ARM: 6352/1: perf: fix event validation

    The validate_event function in the ARM perf events backend has the
    following problems:

    1.) Events that are disabled count towards the cost.
    2.) Events associated with other PMUs [for example, software events or
        breakpoints] do not count towards the cost, but do fail validation,
        causing the group to fail.

    This patch changes validate_event so that it ignores events in the
    PERF_EVENT_STATE_OFF state or that are scheduled for other PMUs.

Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
To: a.p.zijlstra@chello.nl
To: fweisbec@gmail.com
To: will.deacon@arm.com
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: wuzhangjin@gmail.com
Cc: paulus@samba.org
Cc: mingo@elte.hu
Cc: acme@redhat.com
Cc: dengcheng.zhu@gmail.com
Cc: matt@console-pimps.org
Cc: sshtylyov@mvista.com
Cc: ddaney@caviumnetworks.com
Patchwork: http://patchwork.linux-mips.org/patch/2013/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

There are 5 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 arch/mips/kernel/perf_event.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/perf_event.c b/arch/mips/kernel/perf_event.c
index 1ee44a3..3d557611 100644
--- a/arch/mips/kernel/perf_event.c
+++ b/arch/mips/kernel/perf_event.c
@@ -486,8 +486,9 @@ static int validate_event(struct cpu_hw_events *cpuc,
 {
    struct hw_perf_event fake_hwc = event->hw;

-   if (event->pmu && event->pmu != &pmu)
-       return 0;
+   /* Allow mixed event group. So return 1 to pass validation. */
+   if (event->pmu != &pmu || event->state <= PERF_EVENT_STATE_OFF)
+       return 1;

    return mipspmu->alloc_counter(cpuc, &fake_hwc) >= 0;
 }

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