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@@ -70,6 +70,31 @@ static void efi_udelay ( unsigned long usecs ) {
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*/
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static unsigned long efi_currticks ( void ) {
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+ /* EFI provides no clean way for device drivers to shut down
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+ * in preparation for handover to a booted operating system.
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+ * The platform firmware simply doesn't bother to call the
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+ * drivers' Stop() methods. Instead, drivers must register an
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+ * EVT_SIGNAL_EXIT_BOOT_SERVICES event to be signalled when
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+ * ExitBootServices() is called, and clean up without any
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+ * reference to the EFI driver model.
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+ *
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+ * Unfortunately, all timers silently stop working when
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+ * ExitBootServices() is called. Even more unfortunately, and
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+ * for no discernible reason, this happens before any
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+ * EVT_SIGNAL_EXIT_BOOT_SERVICES events are signalled. The
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+ * net effect of this entertaining design choice is that any
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+ * timeout loops on the shutdown path (e.g. for gracefully
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+ * closing outstanding TCP connections) may wait indefinitely.
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+ *
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+ * There is no way to report failure from currticks(), since
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+ * the API lazily assumes that the host system continues to
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+ * travel through time in the usual direction. Work around
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+ * EFI's violation of this assumption by falling back to a
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+ * simple free-running monotonic counter.
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+ */
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+ if ( efi_shutdown_in_progress )
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+ efi_jiffies++;
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+
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return efi_jiffies;
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}
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