On 2020/11/27 上午12:35, Sebastian Andrzej Siewior wrote:
On 2020-11-25 22:28:58 [+0800], zqiu2000@xxxxxxx wrote:
From: Zanxiong Qiu <zqiu2000@xxxxxxx>
get_cpu_var() calls preempt_disable(), while on RT kernel,
pagevec_lru_move_fn() will call spinlock and might schedule
the context out and hence the schedule bug occurred, issue
is found on 5.4.70-rt40 and reproducable on 5.4.74-rt41.
…
2154a0abcc9 ("mm: Revert the DEFINE_PER_CPU_PAGEVEC implementation")
reverted the lock/unlock_swap_pvec function, however, get_cpu_var()
was added back in deactivate_page(), actually, get_locked_var()
shall be used instead to avoid preempt_disable() call for RT.
The commit is
32154a0abcc97 ("mm: Revert the DEFINE_PER_CPU_PAGEVEC implementation")
the reasoning is correct. deactivate_page() was added in v5.4 and I
missed that part when I added back the old patches which did not handle
it :/
Acked-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
My bad, will correct the commit msg and resend, thanks.
Signed-off-by: Zanxiong Qiu <zqiu2000@xxxxxxx>
---
mm/swap.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/swap.c b/mm/swap.c
index cdb4f1fa3a48..463cac334fcf 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -666,12 +666,13 @@ void deactivate_file_page(struct page *page)
void deactivate_page(struct page *page)
{
if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) {
- struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);
+ struct pagevec *pvec = &get_locked_var(swapvec_lock,
+ lru_deactivate_pvecs);
get_page(page);
if (!pagevec_add(pvec, page) || PageCompound(page))
pagevec_lru_move_fn(pvec, lru_deactivate_fn, NULL);
- put_cpu_var(lru_deactivate_pvecs);
+ put_locked_var(swapvec_lock, lru_deactivate_pvecs);
}
}
Sebastian
