blob: 6310bd83f527ef1b73cd3dffb1c45a21d366b786 [file] [log] [blame]
From cc0003c3922a9d7c7a1f3675c2c377a7900c9652 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Tue, 3 Dec 2019 13:35:24 -0500
Subject: [PATCH] psi: Fix a division error in psi poll()
commit c3466952ca1514158d7c16c9cfc48c27d5c5dc0f upstream.
The psi window size is a u64 an can be up to 10 seconds right now,
which exceeds the lower 32 bits of the variable. We currently use
div_u64 for it, which is meant only for 32-bit divisors. The result is
garbage pressure sampling values and even potential div0 crashes.
Use div64_u64.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Jingfeng Xie <xiejingfeng@linux.alibaba.com>
Link: https://lkml.kernel.org/r/20191203183524.41378-3-hannes@cmpxchg.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 970db4686dd4..ce8f6748678a 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -482,7 +482,7 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
u32 remaining;
remaining = win->size - elapsed;
- growth += div_u64(win->prev_growth * remaining, win->size);
+ growth += div64_u64(win->prev_growth * remaining, win->size);
}
return growth;
--
2.7.4