linux-kernel - [PATCH] psi:fix divide by zero in psi_update

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Message-ID: <C377A5F1-F86F-4A27-966F-0285EC6EA934@linux.alibaba.com>
Date:   Fri, 08 Nov 2019 15:33:24 +0800
From:   tim <xiejingfeng@...ux.alibaba.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
CC:     <linux-kernel@...r.kernel.org>
Subject: [PATCH] psi:fix divide by zero in psi_update_stats

In psi_update_stats, it is possible that period has value like
0xXXXXXXXX00000000 where the lower 32 bit is 0, then it calls div_u64 which
truncates u64 period to u32, results in zero divisor.
Use div64_u64() instead of div_u64()  if the divisor is u64 to avoid
truncation to 32-bit on 64-bit platforms.

Signed-off-by: xiejingfeng <xiejingfeng@...ux.alibaba.com>
---
 kernel/sched/psi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 517e3719027e..399d6f106de5 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -291,7 +291,7 @@ static void calc_avgs(unsigned long avg[3], int missed_periods,
 	}
 
 	/* Sample the most recent active period */
-	pct = div_u64(time * 100, period);
+	pct = div64_u64(time * 100, period);
 	pct *= FIXED_1;
 	avg[0] = calc_load(avg[0], EXP_10s, pct);
 	avg[1] = calc_load(avg[1], EXP_60s, pct);
-- 
2.14.4.44.g2045bb