Messages in this thread | | | Date | Tue, 23 Aug 2005 00:18:43 -0700 | From | Tony Lindgren <> | Subject | Re: CONFIG_PRINTK_TIME woes |
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* Andrew Morton <akpm@osdl.org> [050821 02:15]: > "Luck, Tony" <tony.luck@intel.com> wrote: > > > > It has been pointed out to me that ia64 doesn't boot > > with CONFIG_PRINTK_TIME=y. The issue is the call to > > sched_clock() ... which on ia64 accesses some per-cpu > > data to adjust for possible variations in processor > > speed between different cpus. Since the per-cpu page > > is not set up for the first few printk() calls, we die. > > > > Is this an issue on any other architecture? Most versions > > of sched_clock() seem to just scale jiffies into nanoseconds, > > so I guess they don't. s390, sparc64, x86 and x86_64 all > > have more sophisticated versions but they don't appear to me > > to have limitations on how early they might be called.
CONFIG_PRINTK_TIME also has a problem on at least ARM OMAP where the IO mapping to read the clock may not be initialized when sched_clock() is called for the first time.
I'd hate to have to test for something for CONFIG_PRINTK_TIME every time sched_clock() is being called.
The quick fix would seem to be to only allow CONFIG_PRINTK_TIME from kernel cmdline to make it happen a bit later. So basically make int printk_time = 0 until command line is evaluated.
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