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Date: Tue, 19 Mar 2019 04:10:51 -0700
From: tip-bot for Peter Zijlstra <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: rafael.j.wysocki@...el.com, riel@...riel.com,
dave.hansen@...ux.intel.com, rjw@...ysocki.net,
linux-kernel@...r.kernel.org, quentin.perret@....com, bp@...en8.de,
peterz@...radead.org, hpa@...or.com, luto@...nel.org,
zhang.lyra@...il.com, mingo@...nel.org, tglx@...utronix.de,
torvalds@...ux-foundation.org, vincent.wang@...soc.com
Subject: [tip:sched/urgent] sched/cpufreq: Fix 32-bit math overflow
Commit-ID: a23314e9d88d89d49e69db08f60b7caa470f04e1
Gitweb: https://git.kernel.org/tip/a23314e9d88d89d49e69db08f60b7caa470f04e1
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Tue, 5 Mar 2019 09:32:02 +0100
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 19 Mar 2019 12:06:11 +0100
sched/cpufreq: Fix 32-bit math overflow
Vincent Wang reported that get_next_freq() has a mult overflow bug on
32-bit platforms in the IOWAIT boost case, since in that case {util,max}
are in freq units instead of capacity units.
Solve this by moving the IOWAIT boost to capacity units. And since this
means @max is constant; simplify the code.
Reported-by: Vincent Wang <vincent.wang@...soc.com>
Tested-by: Vincent Wang <vincent.wang@...soc.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Chunyan Zhang <zhang.lyra@...il.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Quentin Perret <quentin.perret@....com>
Cc: Rafael J. Wysocki <rjw@...ysocki.net>
Cc: Rik van Riel <riel@...riel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: https://lkml.kernel.org/r/20190305083202.GU32494@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
kernel/sched/cpufreq_schedutil.c | 59 +++++++++++++++++-----------------------
1 file changed, 25 insertions(+), 34 deletions(-)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 033ec7c45f13..1ccf77f6d346 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -48,10 +48,10 @@ struct sugov_cpu {
bool iowait_boost_pending;
unsigned int iowait_boost;
- unsigned int iowait_boost_max;
u64 last_update;
unsigned long bw_dl;
+ unsigned long min;
unsigned long max;
/* The field below is for single-CPU policies only: */
@@ -303,8 +303,7 @@ static bool sugov_iowait_reset(struct sugov_cpu *sg_cpu, u64 time,
if (delta_ns <= TICK_NSEC)
return false;
- sg_cpu->iowait_boost = set_iowait_boost
- ? sg_cpu->sg_policy->policy->min : 0;
+ sg_cpu->iowait_boost = set_iowait_boost ? sg_cpu->min : 0;
sg_cpu->iowait_boost_pending = set_iowait_boost;
return true;
@@ -344,14 +343,13 @@ static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
/* Double the boost at each request */
if (sg_cpu->iowait_boost) {
- sg_cpu->iowait_boost <<= 1;
- if (sg_cpu->iowait_boost > sg_cpu->iowait_boost_max)
- sg_cpu->iowait_boost = sg_cpu->iowait_boost_max;
+ sg_cpu->iowait_boost =
+ min_t(unsigned int, sg_cpu->iowait_boost << 1, SCHED_CAPACITY_SCALE);
return;
}
/* First wakeup after IO: start with minimum boost */
- sg_cpu->iowait_boost = sg_cpu->sg_policy->policy->min;
+ sg_cpu->iowait_boost = sg_cpu->min;
}
/**
@@ -373,47 +371,38 @@ static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
* This mechanism is designed to boost high frequently IO waiting tasks, while
* being more conservative on tasks which does sporadic IO operations.
*/
-static void sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
- unsigned long *util, unsigned long *max)
+static unsigned long sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
+ unsigned long util, unsigned long max)
{
- unsigned int boost_util, boost_max;
+ unsigned long boost;
/* No boost currently required */
if (!sg_cpu->iowait_boost)
- return;
+ return util;
/* Reset boost if the CPU appears to have been idle enough */
if (sugov_iowait_reset(sg_cpu, time, false))
- return;
+ return util;
- /*
- * An IO waiting task has just woken up:
- * allow to further double the boost value
- */
- if (sg_cpu->iowait_boost_pending) {
- sg_cpu->iowait_boost_pending = false;
- } else {
+ if (!sg_cpu->iowait_boost_pending) {
/*
- * Otherwise: reduce the boost value and disable it when we
- * reach the minimum.
+ * No boost pending; reduce the boost value.
*/
sg_cpu->iowait_boost >>= 1;
- if (sg_cpu->iowait_boost < sg_cpu->sg_policy->policy->min) {
+ if (sg_cpu->iowait_boost < sg_cpu->min) {
sg_cpu->iowait_boost = 0;
- return;
+ return util;
}
}
+ sg_cpu->iowait_boost_pending = false;
+
/*
- * Apply the current boost value: a CPU is boosted only if its current
- * utilization is smaller then the current IO boost level.
+ * @util is already in capacity scale; convert iowait_boost
+ * into the same scale so we can compare.
*/
- boost_util = sg_cpu->iowait_boost;
- boost_max = sg_cpu->iowait_boost_max;
- if (*util * boost_max < *max * boost_util) {
- *util = boost_util;
- *max = boost_max;
- }
+ boost = (sg_cpu->iowait_boost * max) >> SCHED_CAPACITY_SHIFT;
+ return max(boost, util);
}
#ifdef CONFIG_NO_HZ_COMMON
@@ -460,7 +449,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
util = sugov_get_util(sg_cpu);
max = sg_cpu->max;
- sugov_iowait_apply(sg_cpu, time, &util, &max);
+ util = sugov_iowait_apply(sg_cpu, time, util, max);
next_f = get_next_freq(sg_policy, util, max);
/*
* Do not reduce the frequency if the CPU has not been idle
@@ -500,7 +489,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
j_util = sugov_get_util(j_sg_cpu);
j_max = j_sg_cpu->max;
- sugov_iowait_apply(j_sg_cpu, time, &j_util, &j_max);
+ j_util = sugov_iowait_apply(j_sg_cpu, time, j_util, j_max);
if (j_util * max > j_max * util) {
util = j_util;
@@ -837,7 +826,9 @@ static int sugov_start(struct cpufreq_policy *policy)
memset(sg_cpu, 0, sizeof(*sg_cpu));
sg_cpu->cpu = cpu;
sg_cpu->sg_policy = sg_policy;
- sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq;
+ sg_cpu->min =
+ (SCHED_CAPACITY_SCALE * policy->cpuinfo.min_freq) /
+ policy->cpuinfo.max_freq;
}
for_each_cpu(cpu, policy->cpus) {
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