forge/linux-uconsole
1
0
Fork 0
Code Issues 1 Pull requests Projects Releases Packages Wiki Activity Actions

UPSTREAM: psi: Fix a division error in psi poll()

Browse source 
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: Sasha Levin <sashal@kernel.org>

(cherry picked from commit c3466952ca)

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I49fdfd55751d1a2cde19666624c9c5d76dc78dad
This commit is contained in:
Johannes Weiner 2019-12-03 13:35:24 -05:00 • committed by Suren Baghdasaryan
commit cf46cf40bc
1 changed files with 1 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

2
kernel/sched/psi.c
View file

@ -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;