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Date: Tue, 7 Oct 2014 16:20:17 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Andreas Schwab <schwab@...ux-m68k.org>, Frederic Weisbecker <fweisbec@...il.com>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, Mark Brown <broonie@...nel.org> Subject: [PATCH 3.10 12/13] cpufreq: Fix wrong time unit conversion 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andreas Schwab <schwab@...ux-m68k.org> commit a857c0b9e24e39fe5be82451b65377795f9538d8 upstream. The time spent by a CPU under a given frequency is stored in jiffies unit in the cpu var cpufreq_stats_table->time_in_state[i], i being the index of the frequency. This is what is displayed in the following file on the right column: cat /sys/devices/system/cpu/cpuX/cpufreq/stats/time_in_state 2301000 19835820 2300000 3172 [...] Now cpufreq converts this jiffies unit delta to clock_t before returning it to the user as in the above file. And that conversion is achieved using the API cputime64_to_clock_t(). Although it accidentally works on traditional tick based cputime accounting, where cputime_t maps directly to jiffies, it doesn't work with other types of cputime accounting such as CONFIG_VIRT_CPU_ACCOUNTING_* where cputime_t can map to nsecs or any granularity preffered by the architecture. For example we get a buggy zero delta on full dyntick configurations: cat /sys/devices/system/cpu/cpuX/cpufreq/stats/time_in_state 2301000 0 2300000 0 [...] Fix this with using the proper jiffies_64_t to clock_t conversion. Reported-and-tested-by: Carsten Emde <C.Emde@...dl.org> Signed-off-by: Andreas Schwab <schwab@...ux-m68k.org> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com> Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com> Cc: Mark Brown <broonie@...nel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/cpufreq/cpufreq_stats.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/cpufreq/cpufreq_stats.c +++ b/drivers/cpufreq/cpufreq_stats.c @@ -81,7 +81,7 @@ static ssize_t show_time_in_state(struct for (i = 0; i < stat->state_num; i++) { len += sprintf(buf + len, "%u %llu\n", stat->freq_table[i], (unsigned long long) - cputime64_to_clock_t(stat->time_in_state[i])); + jiffies_64_to_clock_t(stat->time_in_state[i])); } return len; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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