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63732c2f37
linux/include/asm-i386
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Matt Mackall 63732c2f37 [PATCH] RTC: Remove RTC UIP synchronization on x86 
Reading the CMOS clock on x86 and some other arches currently takes up to one
second because it synchronizes with the CMOS second tick-over.  This delay
shows up at boot time as well a resume time.

This is the currently the most substantial boot time delay for machines that
are working towards instant-on capability.  Also, a quick back of the envelope
calculation (.5sec * 2M users * 1 boot a day * 10 years) suggests it has cost
Linux users in the neighborhood of a million man-hours.

An earlier thread on this topic is here:

http://groups.google.com/group/linux.kernel/browse_frm/thread/8a24255215ff6151/2aa97e66a977653d?hl=en&lr=&ie=UTF-8&rnum=1&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26selm%3D1To2R-2S7-11%40gated-at.bofh.it#2aa97e66a977653d

..from which the consensus seems to be that it's no longer desirable.

In my view, there are basically four cases to consider:

1) networked, need precise walltime: use NTP
2) networked, don't need precise walltime: use NTP anyway
3) not networked, don't need sub-second precision walltime: don't care
4) not networked, need sub-second precision walltime:
   get a network or a radio time source because RTC isn't good enough anyway

So this patch series simply removes the synchronization in favor of a simple
seqlock-like approach using the seconds value.

Note that for purposes of timer accuracy on wakeup, this patch will cause us
to fire timers up to one second late.  But as the current timer resume code
will already sync once (or more!), it's no worse for short timers.

Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Andi Kleen <ak@muc.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kazumoto Kojima <kkojima@rr.iij4u.or.jp>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-28 09:16:00 -08:00
..
mach-bigsmp [PATCH] x86: convert bigsmp to use flat physical mode 2006-01-06 08:33:37 -08:00
mach-default [PATCH] RTC: Remove RTC UIP synchronization on x86 2006-03-28 09:16:00 -08:00
mach-es7000 [PATCH] Compilation fix for ES7000 when no ACPI is specified in config (i386) 2006-03-23 07:38:04 -08:00
mach-generic [PATCH] x86: sutomatically enable bigsmp when we have more than 8 CPUs 2005-09-05 00:06:10 -07:00
mach-numaq [PATCH] Do not enforce unique IO_APIC_ID check for xAPIC systems (i386) 2005-06-23 09:45:09 -07:00
mach-summit [PATCH] USB: Always do usb-handoff 2005-10-28 16:47:49 -07:00
mach-visws [PATCH] i386: fix uses of user_mode() vs. user_mode_vm() 2006-03-23 07:38:05 -08:00
mach-voyager [PATCH] i386: fix uses of user_mode() vs. user_mode_vm() 2006-03-23 07:38:05 -08:00
8253pit.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
a.out.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
acpi.h [PATCH] don't call check_acpi_pci() on x86 with ACPI disabled 2006-03-22 07:53:54 -08:00
agp.h [PATCH] i386: inline asm cleanup 2005-09-05 00:06:11 -07:00
alternative.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
apic.h [PATCH] i386: port ATI timer fix from x86_64 to i386 II 2006-03-08 18:10:31 -08:00
apicdef.h [PATCH] x86: sutomatically enable bigsmp when we have more than 8 CPUs 2005-09-05 00:06:10 -07:00
arch_hooks.h [PATCH] x86: early printk handling fixes 2006-03-23 07:38:05 -08:00
atomic.h [PATCH] atomic: add_unless cmpxchg optimise 2006-03-23 07:38:17 -08:00
auxvec.h [PATCH] auxiliary vector cleanups 2005-09-07 16:57:21 -07:00
bitops.h [PATCH] bitops: i386: use generic bitops 2006-03-26 08:57:12 -08:00
boot.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
bug.h [PATCH] remove all kernel BUGs 2005-05-01 08:59:01 -07:00
bugs.h [PATCH] i386: move SIMD initialization 2006-01-06 08:33:34 -08:00
byteorder.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
cache.h [PATCH] Move read_mostly definition to asm/cache.h 2006-03-23 07:38:10 -08:00
cacheflush.h [PATCH] x86/x86_64: mark rodata section read only: x86 parts 2006-01-06 08:33:36 -08:00
checksum.h [NET]: Fix ipl=>ihl typo in ip_fast_csum 2005-08-29 16:02:48 -07:00
cpu.h [PATCH] i386 CPU hotplug 2005-06-25 16:24:29 -07:00
cpufeature.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
cputime.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
current.h [PATCH] mark several functions __always_inline 2006-01-14 18:27:15 -08:00
debugreg.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
delay.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
desc.h [PATCH] x86: fix broken SMP boot sequence 2006-02-24 14:31:38 -08:00
div64.h [PATCH] include/asm-i386/: "extern inline" -> "static inline" 2005-09-10 10:06:34 -07:00
dma-mapping.h [PATCH] i386: make pci_map_single/pci_map_sg warn for zero length. 2006-01-11 19:04:56 -08:00
dma.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
dmi.h [PATCH] x86_64: Implement early DMI scanning 2006-03-25 09:10:55 -08:00
e820.h [PATCH] Increase number of e820 entries hard limit from 32 to 128 2005-05-01 08:58:51 -07:00
edac.h [PATCH] EDAC: core EDAC support code 2006-01-18 19:20:31 -08:00
elf.h [PATCH] fix remaining missing includes 2005-11-07 07:53:41 -08:00
emergency-restart.h [PATCH] i386: Implement machine_emergency_reboot 2005-07-26 14:35:42 -07:00
errno.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
fcntl.h [PATCH] Clean up struct flock64 definitions 2005-09-07 16:57:38 -07:00
fixmap.h [ACPI] delete CONFIG_ACPI_BOOT 2005-08-24 12:08:54 -04:00
floppy.h [PATCH] make some things static 2005-05-05 16:36:47 -07:00
futex.h [PATCH] lightweight robust futexes updates 2006-03-27 08:44:49 -08:00
genapic.h [PATCH] Do not enforce unique IO_APIC_ID check for xAPIC systems (i386) 2005-06-23 09:45:09 -07:00
hardirq.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
highmem.h [PATCH] kdump: Routines for copying dump pages 2005-06-25 16:24:53 -07:00
hpet.h [PATCH] i386: fix hpet for systems that don't support legacy replacement 2005-05-01 08:58:50 -07:00
hw_irq.h Revert "i386: move apic init in init_IRQs" 2005-10-31 19:16:17 -08:00
i387.h [PATCH] i386: task_thread_info() 2006-01-12 09:08:51 -08:00
i8253.h [PATCH] x86: i8253/i8259A lock cleanup 2005-06-30 08:45:10 -07:00
i8259.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ide.h [PATCH] ide: explain the PCI bus test we do in <asm-i386/ide.h> 2005-11-10 00:10:37 +01:00
io_apic.h [ACPI] delete CONFIG_ACPI_BOOT 2005-08-24 12:08:54 -04:00
io.h [PATCH] remove ISA legacy functions: remove the helpers 2006-03-24 07:33:19 -08:00
ioctl.h [PATCH] Generic ioctl.h 2006-01-10 08:01:34 -08:00
ioctls.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ipc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ipcbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
irq.h [PATCH] Make vm86 support optional 2006-01-08 20:14:11 -08:00
ist.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
kdebug.h [PATCH] Notifier chain update: API changes 2006-03-27 08:44:50 -08:00
kexec.h [PATCH] Kdump: i386 compiler warning fix 2006-01-10 08:01:27 -08:00
kmap_types.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
kprobes.h [PATCH] x86: kprobes-booster 2006-03-26 08:57:04 -08:00
ldt.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
linkage.h [PATCH] i386: fix prevent_tail_call 2005-05-26 16:16:16 -07:00
local.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
math_emu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mc146818rtc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mca_dma.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mca.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mman.h [PATCH] add asm-generic/mman.h 2006-02-15 15:32:22 -08:00
mmu_context.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmx.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmzone.h [PATCH] unify pfn_to_page: i386 pfn_to_page 2006-03-27 08:44:44 -08:00
module.h [PATCH] Base support for AMD Geode GX/LX processors 2006-01-06 08:33:38 -08:00
mpspec_def.h [PATCH] mpspec: remove unneeded packed attribute 2006-01-06 08:33:39 -08:00
mpspec.h [PATCH] i386: remove duplicate declaration of mp_bus_id_to_pci_bus 2006-03-23 07:38:04 -08:00
msgbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
msi.h [PATCH] PCI: Change MSI to use physical delivery mode always 2005-11-10 16:09:18 -08:00
msr.h [PATCH] x86: more asm cleanups 2005-09-05 00:06:12 -07:00
mtrr.h [PATCH] Fix the imlicit declaration of mtrr_centaur_report_mcr in arch/i386/kernel/cpu/centaur.c 2006-03-23 07:38:06 -08:00
mutex.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
namei.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
nmi.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
node.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
numa.h [PATCH] x86-64: Use ACPI PXM to parse PCI<->node assignments 2005-09-12 10:49:57 -07:00
numaq.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
numnodes.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
page.h [PATCH] unify pfn_to_page: i386 pfn_to_page 2006-03-27 08:44:44 -08:00
param.h [PATCH] Avoid namespace pollution in <asm/param.h> 2006-01-02 08:38:38 -08:00
parport.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pci-direct.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pci.h Revert PCIBIOS_MIN_IO changes for 2.6.13 2005-08-14 18:21:30 -07:00
percpu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgalloc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgtable-2level-defs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgtable-2level.h [PATCH] i386: actively synchronize vmalloc area when registering certain callbacks 2006-03-23 07:38:05 -08:00
pgtable-3level-defs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgtable-3level.h [PATCH] i386: actively synchronize vmalloc area when registering certain callbacks 2006-03-23 07:38:05 -08:00
pgtable.h [PATCH] Enable mprotect on huge pages 2006-03-22 07:54:03 -08:00
poll.h [PATCH] POLLRDHUP/EPOLLRDHUP handling for half-closed devices notifications 2006-03-25 08:22:56 -08:00
posix_types.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
processor.h [PATCH] sched: new sched domain for representing multi-core 2006-03-27 08:44:43 -08:00
ptrace.h [PATCH] PTRACE_SYSEMU is only for i386 and clashes with other ptrace codes of other archs 2006-01-08 20:14:04 -08:00
resource.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
rtc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
rwlock.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
rwsem.h [PATCH] add sem_is_read/write_locked() 2005-10-29 21:40:35 -07:00
scatterlist.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
seccomp.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sections.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
segment.h [PATCH] x86: Pnp segments in segment h 2006-01-06 08:33:34 -08:00
semaphore.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
sembuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
serial.h [PATCH] Serial: Split 8250 port table (part 2) 2005-06-29 18:45:19 +01:00
setup.h [PATCH] unify PFN_* macros 2006-03-27 08:44:48 -08:00
shmbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
shmparam.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sigcontext.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
siginfo.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
signal.h [PATCH] Handle TIF_RESTORE_SIGMASK for i386 2006-01-18 19:20:29 -08:00
smp.h [PATCH] PCI: Change MSI to use physical delivery mode always 2005-11-10 16:09:18 -08:00
socket.h [NET]: Introduce SO_{SND,RCV}BUFFORCE socket options 2005-08-29 15:31:35 -07:00
sockios.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sparsemem.h [PATCH] sparsemem memory model for i386 2005-06-23 09:45:05 -07:00
spinlock_types.h [PATCH] spinlock consolidation 2005-09-10 10:06:21 -07:00
spinlock.h [PATCH] i386 spinlocks: disable interrupts only if we enabled them 2006-03-23 07:38:06 -08:00
srat.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
stat.h [PATCH] 2TB files: st_blocks is invalid when calling stat64 2006-03-26 08:57:00 -08:00
statfs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
string.h [PATCH] mark several functions __always_inline 2006-01-14 18:27:15 -08:00
suspend.h [PATCH] i386: Use loaddebug macro consistently 2005-04-16 15:24:46 -07:00
system.h [PATCH] kill include/linux/platform.h, default_idle() cleanup 2006-03-24 07:33:21 -08:00
termbits.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
termios.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
thread_info.h [PATCH] i386: fix singlestepping though a syscall 2006-02-17 08:55:21 -08:00
timer.h [PATCH] add suspend/resume for timer 2005-09-05 00:06:18 -07:00
timex.h [PATCH] x86: cpu_khz type fix 2005-06-23 09:45:11 -07:00
tlb.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
tlbflush.h [PATCH] seccomp: tsc disable 2005-06-27 15:11:44 -07:00
topology.h [PATCH] sched: new sched domain for representing multi-core 2006-03-27 08:44:43 -08:00
types.h [PATCH] 2TB files: add blkcnt_t 2006-03-26 08:57:00 -08:00
uaccess.h [PATCH] i386: Add a temporary to make put_user more type safe 2006-03-23 07:38:04 -08:00
ucontext.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
unaligned.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
unistd.h [PATCH] lightweight robust futexes: i386 2006-03-27 08:44:49 -08:00
user.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
vga.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
vic.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
vm86.h [PATCH] Make vm86 support optional 2006-01-08 20:14:11 -08:00
voyager.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
xor.h [PATCH] i386: inline asm cleanup 2005-09-05 00:06:11 -07:00