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[67.170.153.23]) by mx.google.com with ESMTPSA id x1sm3070268pdp.1.2015.03.11.21.16.46 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 11 Mar 2015 21:16:46 -0700 (PDT) From: John Stultz To: lkml Cc: John Stultz , Dave Jones , Linus Torvalds , Thomas Gleixner , Richard Cochran , Prarit Bhargava , Stephen Boyd , Ingo Molnar , Peter Zijlstra Subject: [PATCH 03/12] clocksource: Add max_cycles to clocksource structure Date: Wed, 11 Mar 2015 21:16:31 -0700 Message-Id: <1426133800-29329-4-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1426133800-29329-1-git-send-email-john.stultz@linaro.org> References: <1426133800-29329-1-git-send-email-john.stultz@linaro.org> X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: john.stultz@linaro.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.215.45 as permitted sender) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Precedence: list Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org List-ID: X-Google-Group-Id: 836684582541 List-Post: , List-Help: , List-Archive: List-Unsubscribe: , In order to facilitate some clocksource validation, add a max_cycles entry to the structure which will hold the maximum cycle value that can safely be multiplied without potentially causing an overflow. Cc: Dave Jones Cc: Linus Torvalds Cc: Thomas Gleixner Cc: Richard Cochran Cc: Prarit Bhargava Cc: Stephen Boyd Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: John Stultz --- include/linux/clocksource.h | 6 ++++-- kernel/time/clocksource.c | 29 +++++++++++++++++------------ kernel/time/sched_clock.c | 2 +- 3 files changed, 22 insertions(+), 15 deletions(-) diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index 9c78d15..63fe52f 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -56,6 +56,7 @@ struct module; * @shift: cycle to nanosecond divisor (power of two) * @max_idle_ns: max idle time permitted by the clocksource (nsecs) * @maxadj: maximum adjustment value to mult (~11%) + * @max_cycles: maximum safe cycle value which won't overflow on mult * @flags: flags describing special properties * @archdata: arch-specific data * @suspend: suspend function for the clocksource, if necessary @@ -76,7 +77,7 @@ struct clocksource { #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA struct arch_clocksource_data archdata; #endif - + u64 max_cycles; const char *name; struct list_head list; int rating; @@ -189,7 +190,8 @@ extern struct clocksource * __init clocksource_default_clock(void); extern void clocksource_mark_unstable(struct clocksource *cs); extern u64 -clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask); +clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, + u64 *max_cycles); extern void clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec); diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index fe64c7f..a491803 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -469,11 +469,14 @@ static u32 clocksource_max_adjustment(struct clocksource *cs) * @shift: cycle to nanosecond divisor (power of two) * @maxadj: maximum adjustment value to mult (~11%) * @mask: bitmask for two's complement subtraction of non 64 bit counters + * @max_cyc: maximum cycle value before potential overflow (does not include + * any safety margin) * * NOTE: This function includes a safety margin of 50%, so that bad clock values * can be detected. */ -u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask) +u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, + u64 *max_cyc) { u64 max_nsecs, max_cycles; @@ -493,6 +496,10 @@ u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask) max_cycles = min(max_cycles, mask); max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift); + /* return the max_cycles value as well if requested */ + if (max_cyc) + *max_cyc = max_cycles; + /* Return 50% of the actual maximum, so we can detect bad values */ max_nsecs >>= 1; @@ -500,17 +507,15 @@ u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask) } /** - * clocksource_max_deferment - Returns max time the clocksource should be deferred - * @cs: Pointer to clocksource + * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles + * @cs: Pointer to clocksource to be updated * */ -static u64 clocksource_max_deferment(struct clocksource *cs) +static inline void clocksource_update_max_deferment(struct clocksource *cs) { - u64 max_nsecs; - - max_nsecs = clocks_calc_max_nsecs(cs->mult, cs->shift, cs->maxadj, - cs->mask); - return max_nsecs; + cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift, + cs->maxadj, cs->mask, + &cs->max_cycles); } #ifndef CONFIG_ARCH_USES_GETTIMEOFFSET @@ -684,7 +689,7 @@ void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq) cs->maxadj = clocksource_max_adjustment(cs); } - cs->max_idle_ns = clocksource_max_deferment(cs); + clocksource_update_max_deferment(cs); } EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale); @@ -730,8 +735,8 @@ int clocksource_register(struct clocksource *cs) "Clocksource %s might overflow on 11%% adjustment\n", cs->name); - /* calculate max idle time permitted for this clocksource */ - cs->max_idle_ns = clocksource_max_deferment(cs); + /* Update max idle time permitted for this clocksource */ + clocksource_update_max_deferment(cs); mutex_lock(&clocksource_mutex); clocksource_enqueue(cs); diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c index c794b84..d43855b 100644 --- a/kernel/time/sched_clock.c +++ b/kernel/time/sched_clock.c @@ -126,7 +126,7 @@ void __init sched_clock_register(u64 (*read)(void), int bits, new_mask = CLOCKSOURCE_MASK(bits); /* calculate how many ns until we risk wrapping */ - wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask); + wrap = clocks_calc_max_nsecs(new_mult, new_shift, 0, new_mask, NULL); new_wrap_kt = ns_to_ktime(wrap); /* update epoch for new counter and update epoch_ns from old counter*/