linux/kernel/time
Jon Hunter 97813f2fe7 nohz: Allow 32-bit machines to sleep for more than 2.15 seconds
In the dynamic tick code, "max_delta_ns" (member of the
"clock_event_device" structure) represents the maximum sleep time
that can occur between timer events in nanoseconds.

The variable, "max_delta_ns", is defined as an unsigned long
which is a 32-bit integer for 32-bit machines and a 64-bit
integer for 64-bit machines (if -m64 option is used for gcc).
The value of max_delta_ns is set by calling the function
"clockevent_delta2ns()" which returns a maximum value of LONG_MAX.
For a 32-bit machine LONG_MAX is equal to 0x7fffffff and in
nanoseconds this equates to ~2.15 seconds. Hence, the maximum
sleep time for a 32-bit machine is ~2.15 seconds, where as for
a 64-bit machine it will be many years.

This patch changes the type of max_delta_ns to be "u64" instead of
"unsigned long" so that this variable is a 64-bit type for both 32-bit
and 64-bit machines. It also changes the maximum value returned by
clockevent_delta2ns() to KTIME_MAX.  Hence this allows a 32-bit
machine to sleep for longer than ~2.15 seconds. Please note that this
patch also changes "min_delta_ns" to be "u64" too and although this is
unnecessary, it makes the patch simpler as it avoids to fixup all
callers of clockevent_delta2ns().

[ tglx: changed "unsigned long long" to u64 as we use this data type
  	through out the time code ]

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Cc: John Stultz <johnstul@us.ibm.com>
LKML-Reference: <1250617512-23567-3-git-send-email-jon-hunter@ti.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2009-11-13 20:46:24 +01:00
..
clockevents.c nohz: Allow 32-bit machines to sleep for more than 2.15 seconds 2009-11-13 20:46:24 +01:00
clocksource.c nohz: Prevent clocksource wrapping during idle 2009-11-13 20:46:24 +01:00
jiffies.c clocksource: Cleanup clocksource selection 2009-08-15 10:55:46 +02:00
Kconfig Kconfig: eliminate "def_bool n" constructs 2008-10-16 11:21:31 -07:00
Makefile time: add function to convert between calendar time and broken-down time for universal use 2009-09-24 07:20:56 -07:00
ntp.c timekeeping: Introduce timekeeping_leap_insert 2009-08-15 10:55:45 +02:00
tick-broadcast.c clockevent: Prevent dead lock on clockevents_lock 2009-08-19 18:15:10 +02:00
tick-common.c clockevents: prevent endless loop in tick_handle_periodic() 2009-05-02 10:22:27 +02:00
tick-internal.h NOHZ: restart tick device from irq_enter() 2008-10-17 18:13:38 +02:00
tick-oneshot.c nohz: Allow 32-bit machines to sleep for more than 2.15 seconds 2009-11-13 20:46:24 +01:00
tick-sched.c nohz: Track last do_timer() cpu 2009-11-13 20:46:24 +01:00
timecompare.c timecompare: generic infrastructure to map between two time bases 2009-02-15 22:43:32 -08:00
timeconv.c time: add function to convert between calendar time and broken-down time for universal use 2009-09-24 07:20:56 -07:00
timekeeping.c nohz: Prevent clocksource wrapping during idle 2009-11-13 20:46:24 +01:00
timer_list.c nohz: Allow 32-bit machines to sleep for more than 2.15 seconds 2009-11-13 20:46:24 +01:00
timer_stats.c const: constify remaining file_operations 2009-10-01 16:11:11 -07:00