diff options
Diffstat (limited to 'src/interface/efi/efi_timer.c')
| -rw-r--r-- | src/interface/efi/efi_timer.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/src/interface/efi/efi_timer.c b/src/interface/efi/efi_timer.c index da064120a..1fd9971e9 100644 --- a/src/interface/efi/efi_timer.c +++ b/src/interface/efi/efi_timer.c @@ -70,6 +70,31 @@ static void efi_udelay ( unsigned long usecs ) { */ static unsigned long efi_currticks ( void ) { + /* EFI provides no clean way for device drivers to shut down + * in preparation for handover to a booted operating system. + * The platform firmware simply doesn't bother to call the + * drivers' Stop() methods. Instead, drivers must register an + * EVT_SIGNAL_EXIT_BOOT_SERVICES event to be signalled when + * ExitBootServices() is called, and clean up without any + * reference to the EFI driver model. + * + * Unfortunately, all timers silently stop working when + * ExitBootServices() is called. Even more unfortunately, and + * for no discernible reason, this happens before any + * EVT_SIGNAL_EXIT_BOOT_SERVICES events are signalled. The + * net effect of this entertaining design choice is that any + * timeout loops on the shutdown path (e.g. for gracefully + * closing outstanding TCP connections) may wait indefinitely. + * + * There is no way to report failure from currticks(), since + * the API lazily assumes that the host system continues to + * travel through time in the usual direction. Work around + * EFI's violation of this assumption by falling back to a + * simple free-running monotonic counter. + */ + if ( efi_shutdown_in_progress ) + efi_jiffies++; + return efi_jiffies; } |