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05 April 2024, 19:05:47 UTC
Revision 58d4e21e50ff3cc57910a8abc20d7e14375d2f61 authored by Tony Luck on 18 July 2014, 18:43:01 UTC, committed by Steven Rostedt on 21 July 2014, 13:56:12 UTC 
tracing: Fix wraparound problems in "uptime" trace clock
 
The "uptime" trace clock added in:

    commit 8aacf017b065a805d27467843490c976835eb4a5
    tracing: Add "uptime" trace clock that uses jiffies

has wraparound problems when the system has been up more
than 1 hour 11 minutes and 34 seconds. It converts jiffies
to nanoseconds using:
        (u64)jiffies_to_usecs(jiffy) * 1000ULL
but since jiffies_to_usecs() only returns a 32-bit value, it
truncates at 2^32 microseconds.  An additional problem on 32-bit
systems is that the argument is "unsigned long", so fixing the
return value only helps until 2^32 jiffies (49.7 days on a HZ=1000
system).

Avoid these problems by using jiffies_64 as our basis, and
not converting to nanoseconds (we do convert to clock_t because
user facing API must not be dependent on internal kernel
HZ values).

Link: http://lkml.kernel.org/p/99d63c5bfe9b320a3b428d773825a37095bf6a51.1405708254.git.tony.luck@intel.com

Cc: stable@vger.kernel.org # 3.10+
Fixes: 8aacf017b065 "tracing: Add "uptime" trace clock that uses jiffies"
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
1 parent 9a3c414
History
Tip revision: 58d4e21e50ff3cc57910a8abc20d7e14375d2f61 authored by Tony Luck on 18 July 2014, 18:43:01 UTC
tracing: Fix wraparound problems in "uptime" trace clock
Tip revision: 58d4e21
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