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    Subject[RFC][PATCH 10/11] perfcounters: abstract wakeup flag setting in core to fix powerpc build
    From: Paul Mackerras <paulus@samba.org>

    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>
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    ---
    arch/powerpc/include/asm/hw_irq.h | 14 +++++++++++---
    arch/powerpc/kernel/irq.c | 11 +++--------
    arch/powerpc/kernel/perf_counter.c | 3 +--
    arch/x86/include/asm/perf_counter.h | 3 +++
    kernel/perf_counter.c | 2 +-
    5 files changed, 19 insertions(+), 14 deletions(-)

    Index: linux-2.6/arch/powerpc/include/asm/hw_irq.h
    ===================================================================
    --- linux-2.6.orig/arch/powerpc/include/asm/hw_irq.h
    +++ linux-2.6/arch/powerpc/include/asm/hw_irq.h
    @@ -142,10 +142,17 @@ static inline unsigned long get_perf_cou
    return x;
    }

    -static inline void set_perf_counter_pending(int x)
    +static inline void set_perf_counter_pending(void)
    {
    asm volatile("stb %0,%1(13)" : :
    - "r" (x),
    + "r" (1),
    + "i" (offsetof(struct paca_struct, perf_counter_pending)));
    +}
    +
    +static inline void clear_perf_counter_pending(void)
    +{
    + asm volatile("stb %0,%1(13)" : :
    + "r" (0),
    "i" (offsetof(struct paca_struct, perf_counter_pending)));
    }

    @@ -158,7 +165,8 @@ static inline unsigned long get_perf_cou
    return 0;
    }

    -static inline void set_perf_counter_pending(int x) {}
    +static inline void set_perf_counter_pending(void) {}
    +static inline void clear_perf_counter_pending(void) {}
    static inline void perf_counter_do_pending(void) {}
    #endif /* CONFIG_PERF_COUNTERS */

    Index: linux-2.6/arch/powerpc/kernel/irq.c
    ===================================================================
    --- linux-2.6.orig/arch/powerpc/kernel/irq.c
    +++ linux-2.6/arch/powerpc/kernel/irq.c
    @@ -104,13 +104,6 @@ static inline notrace void set_soft_enab
    : : "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(unsig
    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;
    Index: linux-2.6/arch/powerpc/kernel/perf_counter.c
    ===================================================================
    --- linux-2.6.orig/arch/powerpc/kernel/perf_counter.c
    +++ linux-2.6/arch/powerpc/kernel/perf_counter.c
    @@ -653,7 +653,6 @@ void perf_counter_do_pending(void)
    struct cpu_hw_counters *cpuhw = &__get_cpu_var(cpu_hw_counters);
    struct perf_counter *counter;

    - set_perf_counter_pending(0);
    for (i = 0; i < cpuhw->n_counters; ++i) {
    counter = cpuhw->counter[i];
    if (counter && counter->wakeup_pending) {
    @@ -811,7 +810,7 @@ static void perf_counter_interrupt(struc
    perf_counter_do_pending();
    irq_exit();
    } else {
    - set_perf_counter_pending(1);
    + set_perf_counter_pending();
    }
    }
    }
    Index: linux-2.6/arch/x86/include/asm/perf_counter.h
    ===================================================================
    --- linux-2.6.orig/arch/x86/include/asm/perf_counter.h
    +++ linux-2.6/arch/x86/include/asm/perf_counter.h
    @@ -84,6 +84,9 @@ union cpuid10_edx {
    #define MSR_ARCH_PERFMON_FIXED_CTR2 0x30b
    #define X86_PMC_IDX_FIXED_BUS_CYCLES (X86_PMC_IDX_FIXED + 2)

    +#define set_perf_counter_pending() \
    + set_tsk_thread_flag(current, TIF_PERF_COUNTERS);
    +
    #ifdef CONFIG_PERF_COUNTERS
    extern void init_hw_perf_counters(void);
    extern void perf_counters_lapic_init(int nmi);
    Index: linux-2.6/kernel/perf_counter.c
    ===================================================================
    --- linux-2.6.orig/kernel/perf_counter.c
    +++ linux-2.6/kernel/perf_counter.c
    @@ -1438,7 +1438,7 @@ static void perf_swcounter_interrupt(str

    if (nmi) {
    counter->wakeup_pending = 1;
    - set_tsk_thread_flag(current, TIF_PERF_COUNTERS);
    + set_perf_counter_pending();
    } else
    wake_up(&counter->waitq);
    }
    --



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