MIPS, Perf-events: Work with irq_work [Linux 2.6.38]

This Linux kernel change "MIPS, Perf-events: Work with irq_work" 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 16:19:17 2011 +0800. The commit for this change in Linux stable tree is 91f0173 (patch).

MIPS, Perf-events: Work with irq_work

This is the MIPS part of the following commit by Peter Zijlstra:

- e360adbe29241a0194e10e20595360dd7b98a2b3
    irq_work: Add generic hardirq context callbacks

    Provide a mechanism that allows running code in IRQ context. It is
    most useful for NMI code that needs to interact with the rest of the
    system -- like wakeup a task to drain buffers.

    Perf currently has such a mechanism, so extract that and provide it as
    a generic feature, independent of perf so that others may also
    benefit.

    The IRQ context callback is generated through self-IPIs where
    possible, or on architectures like powerpc the decrementer (the
    built-in timer facility) is set to generate an interrupt immediately.

    Architectures that don't have anything like this get to do with a
    callback from the timer tick. These architectures can call
    irq_work_run() at the tail of any IRQ handlers that might enqueue such
    work (like the perf IRQ handler) to avoid undue latencies in
    processing the work.

For MIPSXX, we need to call irq_work_run() at the tail of the perf IRQ
handler as described above.

Reported-by: Wu Zhangjin <wuzhangjin@gmail.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
To: fweisbec@gmail.com
To: will.deacon@arm.com
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: paulus@samba.org
Cc: mingo@elte.hu
Cc: acme@redhat.com
Cc: matt@console-pimps.org
Cc: sshtylyov@mvista.com,
Patchwork: http://patchwork.linux-mips.org/patch/2011/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

There are 15 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 arch/mips/Kconfig                    |  1 +
 arch/mips/include/asm/perf_event.h   | 12 +-----------
 arch/mips/kernel/perf_event_mipsxx.c |  2 +-
 3 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 972695e..bd7b64d 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -4,6 +4,7 @@ config MIPS
    select HAVE_GENERIC_DMA_COHERENT
    select HAVE_IDE
    select HAVE_OPROFILE
+   select HAVE_IRQ_WORK
    select HAVE_PERF_EVENTS
    select PERF_USE_VMALLOC
    select HAVE_ARCH_KGDB
diff --git a/arch/mips/include/asm/perf_event.h b/arch/mips/include/asm/perf_event.h
index e00007c..d0c7749 100644
--- a/arch/mips/include/asm/perf_event.h
+++ b/arch/mips/include/asm/perf_event.h
@@ -11,15 +11,5 @@

 #ifndef __MIPS_PERF_EVENT_H__
 #define __MIPS_PERF_EVENT_H__
-
-/*
- * MIPS performance counters do not raise NMI upon overflow, a regular
- * interrupt will be signaled. Hence we can do the pending perf event
- * work at the tail of the irq handler.
- */
-static inline void
-set_perf_event_pending(void)
-{
-}
-
+/* Leave it empty here. The file is required by linux/perf_event.h */
 #endif /* __MIPS_PERF_EVENT_H__ */
diff --git a/arch/mips/kernel/perf_event_mipsxx.c b/arch/mips/kernel/perf_event_mipsxx.c
index 183e0d2..d45ea37 100644
--- a/arch/mips/kernel/perf_event_mipsxx.c
+++ b/arch/mips/kernel/perf_event_mipsxx.c
@@ -696,7 +696,7 @@ static int mipsxx_pmu_handle_shared_irq(void)
     * interrupt, not NMI.
     */
    if (handled == IRQ_HANDLED)
-       perf_event_do_pending();
+       irq_work_run();

 #ifdef CONFIG_MIPS_MT_SMP
    read_unlock(&pmuint_rwlock);

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