trace: add workaround for SystemTap PR13296
SystemTap sdt.h sometimes results in compiled probes without sufficient information to extract arguments. This can be solved in a slightly hacky way by encouraging the compiler to place arguments into registers. This patch fixes the apic_reset_irq_delivered() trace event on Fedora 20 with gcc-4.8.2-7.fc20 and systemtap-sdt-devel-2.4-2.fc20 on x86_64. Signed-off-by: Frank Ch. Eigler <fche@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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					@ -117,7 +117,12 @@ void apic_report_irq_delivered(int delivered)
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void apic_reset_irq_delivered(void)
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					void apic_reset_irq_delivered(void)
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{
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					{
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    trace_apic_reset_irq_delivered(apic_irq_delivered);
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					    /* Copy this into a local variable to encourage gcc to emit a plain
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					     * register for a sys/sdt.h marker.  For details on this workaround, see:
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					     * https://sourceware.org/bugzilla/show_bug.cgi?id=13296
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					     */
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					    volatile int a_i_d = apic_irq_delivered;
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					    trace_apic_reset_irq_delivered(a_i_d);
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    apic_irq_delivered = 0;
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					    apic_irq_delivered = 0;
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}
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					}
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