* [PATCH] highmem: fix checks in __kmap_local_sched_{in,out}
@ 2022-04-03 23:51 Max Filippov
2022-04-04 15:12 ` Thomas Gleixner
0 siblings, 1 reply; 2+ messages in thread
From: Max Filippov @ 2022-04-03 23:51 UTC (permalink / raw)
To: Thomas Gleixner
Cc: Peter Zijlstra (Intel),
Andrew Morton, linux-mm, linux-kernel, Max Filippov
When CONFIG_DEBUG_KMAP_LOCAL is enabled __kmap_local_sched_{in,out}
check that even slots in the tsk->kmap_ctrl.pteval are unmapped. The
slots are initialized with 0 value, but the check is done with pte_none.
0 pte however does not necessarily mean that pte_none will return true.
e.g. on xtensa it returns false, resulting in the following runtime
warnings:
WARNING: CPU: 0 PID: 101 at mm/highmem.c:627 __kmap_local_sched_out+0x51/0x108
CPU: 0 PID: 101 Comm: touch Not tainted 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
Call Trace:
dump_stack+0xc/0x40
__warn+0x8f/0x174
warn_slowpath_fmt+0x48/0xac
__kmap_local_sched_out+0x51/0x108
__schedule+0x71a/0x9c4
preempt_schedule_irq+0xa0/0xe0
common_exception_return+0x5c/0x93
do_wp_page+0x30e/0x330
handle_mm_fault+0xa70/0xc3c
do_page_fault+0x1d8/0x3c4
common_exception+0x7f/0x7f
WARNING: CPU: 0 PID: 101 at mm/highmem.c:664 __kmap_local_sched_in+0x50/0xe0
CPU: 0 PID: 101 Comm: touch Tainted: G W 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
Call Trace:
dump_stack+0xc/0x40
__warn+0x8f/0x174
warn_slowpath_fmt+0x48/0xac
__kmap_local_sched_in+0x50/0xe0
finish_task_switch$isra$0+0x1ce/0x2f8
__schedule+0x86e/0x9c4
preempt_schedule_irq+0xa0/0xe0
common_exception_return+0x5c/0x93
do_wp_page+0x30e/0x330
handle_mm_fault+0xa70/0xc3c
do_page_fault+0x1d8/0x3c4
common_exception+0x7f/0x7f
Fix it by replacing !pte_none(pteval) with pte_val(pteval) != 0.
Fixes: 5fbda3ecd14a ("sched: highmem: Store local kmaps in task struct")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
mm/highmem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/highmem.c b/mm/highmem.c
index 762679050c9a..916b66e0776c 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -624,7 +624,7 @@ void __kmap_local_sched_out(void)
/* With debug all even slots are unmapped and act as guard */
if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
- WARN_ON_ONCE(!pte_none(pteval));
+ WARN_ON_ONCE(pte_val(pteval) != 0);
continue;
}
if (WARN_ON_ONCE(pte_none(pteval)))
@@ -661,7 +661,7 @@ void __kmap_local_sched_in(void)
/* With debug all even slots are unmapped and act as guard */
if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
- WARN_ON_ONCE(!pte_none(pteval));
+ WARN_ON_ONCE(pte_val(pteval) != 0);
continue;
}
if (WARN_ON_ONCE(pte_none(pteval)))
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] highmem: fix checks in __kmap_local_sched_{in,out}
2022-04-03 23:51 [PATCH] highmem: fix checks in __kmap_local_sched_{in,out} Max Filippov
@ 2022-04-04 15:12 ` Thomas Gleixner
0 siblings, 0 replies; 2+ messages in thread
From: Thomas Gleixner @ 2022-04-04 15:12 UTC (permalink / raw)
To: Max Filippov
Cc: Peter Zijlstra (Intel),
Andrew Morton, linux-mm, linux-kernel, Max Filippov
On Sun, Apr 03 2022 at 16:51, Max Filippov wrote:
> When CONFIG_DEBUG_KMAP_LOCAL is enabled __kmap_local_sched_{in,out}
> check that even slots in the tsk->kmap_ctrl.pteval are unmapped. The
> slots are initialized with 0 value, but the check is done with pte_none.
> 0 pte however does not necessarily mean that pte_none will return true.
> e.g. on xtensa it returns false, resulting in the following runtime
> warnings:
>
> WARNING: CPU: 0 PID: 101 at mm/highmem.c:627 __kmap_local_sched_out+0x51/0x108
> CPU: 0 PID: 101 Comm: touch Not tainted 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
> Call Trace:
> dump_stack+0xc/0x40
> __warn+0x8f/0x174
> warn_slowpath_fmt+0x48/0xac
> __kmap_local_sched_out+0x51/0x108
> __schedule+0x71a/0x9c4
> preempt_schedule_irq+0xa0/0xe0
> common_exception_return+0x5c/0x93
> do_wp_page+0x30e/0x330
> handle_mm_fault+0xa70/0xc3c
> do_page_fault+0x1d8/0x3c4
> common_exception+0x7f/0x7f
>
> WARNING: CPU: 0 PID: 101 at mm/highmem.c:664 __kmap_local_sched_in+0x50/0xe0
> CPU: 0 PID: 101 Comm: touch Tainted: G W 5.17.0-rc7-00010-gd3a1cdde80d2-dirty #13
> Call Trace:
> dump_stack+0xc/0x40
> __warn+0x8f/0x174
> warn_slowpath_fmt+0x48/0xac
> __kmap_local_sched_in+0x50/0xe0
> finish_task_switch$isra$0+0x1ce/0x2f8
> __schedule+0x86e/0x9c4
> preempt_schedule_irq+0xa0/0xe0
> common_exception_return+0x5c/0x93
> do_wp_page+0x30e/0x330
> handle_mm_fault+0xa70/0xc3c
> do_page_fault+0x1d8/0x3c4
> common_exception+0x7f/0x7f
>
> Fix it by replacing !pte_none(pteval) with pte_val(pteval) != 0.
Oops. Sorry.
> Fixes: 5fbda3ecd14a ("sched: highmem: Store local kmaps in task struct")
> Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2022-04-04 15:12 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-04-03 23:51 [PATCH] highmem: fix checks in __kmap_local_sched_{in,out} Max Filippov
2022-04-04 15:12 ` Thomas Gleixner
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).