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authorjohn stultz <johnstul@us.ibm.com>2007-03-05 03:30:50 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-05 10:57:53 -0500
commit6bb74df481223731af6c7e0ff3adb31f6442cfcd (patch)
tree2aa0b0cfa55cb4b9a9236bd94b723d83eb0bdaa8 /include/asm-x86_64/tsc.h
parent4540768011352d38afb89d400eacb3e261507b70 (diff)
[PATCH] clocksource init adjustments (fix bug #7426)
This patch resolves the issue found here: http://bugme.osdl.org/show_bug.cgi?id=7426 The basic summary is: Currently we register most of i386/x86_64 clocksources at module_init time. Then we enable clocksource selection at late_initcall time. This causes some problems for drivers that use gettimeofday for init calibration routines (specifically the es1968 driver in this case), where durring module_init, the only clocksource available is the low-res jiffies clocksource. This may cause slight calibration errors, due to the small sampling time used. It should be noted that drivers that require fine grained time may not function on architectures that do not have better then jiffies resolution timekeeping (there are a few). However, this does not discount the reasonable need for such fine-grained timekeeping at init time. Thus the solution here is to register clocksources earlier (ideally when the hardware is being initialized), and then we enable clocksource selection at fs_initcall (before device_initcall). This patch should probably get some testing time in -mm, since clocksource selection is one of the most important issues for correct timekeeping, and I've only been able to test this on a few of my own boxes. Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/asm-x86_64/tsc.h')
-rw-r--r--include/asm-x86_64/tsc.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/asm-x86_64/tsc.h b/include/asm-x86_64/tsc.h
index 9a0a368852c7..26c3e9828288 100644
--- a/include/asm-x86_64/tsc.h
+++ b/include/asm-x86_64/tsc.h
@@ -55,6 +55,7 @@ static __always_inline cycles_t get_cycles_sync(void)
55extern void tsc_init(void); 55extern void tsc_init(void);
56extern void mark_tsc_unstable(void); 56extern void mark_tsc_unstable(void);
57extern int unsynchronized_tsc(void); 57extern int unsynchronized_tsc(void);
58extern void init_tsc_clocksource(void);
58 59
59/* 60/*
60 * Boot-time check whether the TSCs are synchronized across 61 * Boot-time check whether the TSCs are synchronized across