* kernel BUG at mm/swap_slots.c:270
@ 2017-03-18 16:57 ` Linus Torvalds
0 siblings, 0 replies; 8+ messages in thread
From: Linus Torvalds @ 2017-03-18 16:57 UTC (permalink / raw)
To: Tim Chen, Huang, Ying, Michal Hocko, Andrew Morton
Cc: linux-mm, Linux Kernel Mailing List
Tim at al,
I got this on my desktop at shutdown:
------------[ cut here ]------------
kernel BUG at mm/swap_slots.c:270!
invalid opcode: 0000 [#1] SMP
CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
Hardware name: System manufacturer System Product Name/Z170-K, BIOS
1803 05/06/2016
RIP: 0010:free_swap_slot+0xba/0xd0
Call Trace:
swap_free+0x36/0x40
do_swap_page+0x360/0x6d0
__handle_mm_fault+0x880/0x1080
handle_mm_fault+0xd0/0x240
__do_page_fault+0x232/0x4d0
do_page_fault+0x20/0x70
page_fault+0x22/0x30
---[ end trace aefc9ede53e0ab21 ]---
so there seems to be something screwy in the new swap_slots code.
Any ideas? I'm not finding other reports of this, but I'm also not
seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
much checks whether swap_slot_cache_initialized has been set, so the
BUG_ON() just seems like garbage. But please take a look.
Linus
^ permalink raw reply [flat|nested] 8+ messages in thread
* kernel BUG at mm/swap_slots.c:270
@ 2017-03-18 16:57 ` Linus Torvalds
0 siblings, 0 replies; 8+ messages in thread
From: Linus Torvalds @ 2017-03-18 16:57 UTC (permalink / raw)
To: Tim Chen, Huang, Ying, Michal Hocko, Andrew Morton
Cc: linux-mm, Linux Kernel Mailing List
Tim at al,
I got this on my desktop at shutdown:
------------[ cut here ]------------
kernel BUG at mm/swap_slots.c:270!
invalid opcode: 0000 [#1] SMP
CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
Hardware name: System manufacturer System Product Name/Z170-K, BIOS
1803 05/06/2016
RIP: 0010:free_swap_slot+0xba/0xd0
Call Trace:
swap_free+0x36/0x40
do_swap_page+0x360/0x6d0
__handle_mm_fault+0x880/0x1080
handle_mm_fault+0xd0/0x240
__do_page_fault+0x232/0x4d0
do_page_fault+0x20/0x70
page_fault+0x22/0x30
---[ end trace aefc9ede53e0ab21 ]---
so there seems to be something screwy in the new swap_slots code.
Any ideas? I'm not finding other reports of this, but I'm also not
seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
much checks whether swap_slot_cache_initialized has been set, so the
BUG_ON() just seems like garbage. But please take a look.
Linus
--
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: kernel BUG at mm/swap_slots.c:270
2017-03-18 16:57 ` Linus Torvalds
@ 2017-03-19 14:04 ` Michal Hocko
-1 siblings, 0 replies; 8+ messages in thread
From: Michal Hocko @ 2017-03-19 14:04 UTC (permalink / raw)
To: Linus Torvalds
Cc: Tim Chen, Huang, Ying, Andrew Morton, linux-mm,
Linux Kernel Mailing List
On Sat 18-03-17 09:57:18, Linus Torvalds wrote:
> Tim at al,
> I got this on my desktop at shutdown:
>
> ------------[ cut here ]------------
> kernel BUG at mm/swap_slots.c:270!
> invalid opcode: 0000 [#1] SMP
> CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
> Hardware name: System manufacturer System Product Name/Z170-K, BIOS
> 1803 05/06/2016
> RIP: 0010:free_swap_slot+0xba/0xd0
> Call Trace:
> swap_free+0x36/0x40
> do_swap_page+0x360/0x6d0
> __handle_mm_fault+0x880/0x1080
> handle_mm_fault+0xd0/0x240
> __do_page_fault+0x232/0x4d0
> do_page_fault+0x20/0x70
> page_fault+0x22/0x30
> ---[ end trace aefc9ede53e0ab21 ]---
>
> so there seems to be something screwy in the new swap_slots code.
I am travelling (LSFMM) so I didn't get to look at this more thoroughly
but it seems like a race because enable_swap_slots_cache is called at
the very end of the swapon and we could have already created a swap
entry for a page by that time I guess.
> Any ideas? I'm not finding other reports of this, but I'm also not
> seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
> much checks whether swap_slot_cache_initialized has been set, so the
> BUG_ON() just seems like garbage. But please take a look.
I guess you are right. I cannot speak of the original intention but it
seems Tim wanted to be careful to not see unexpected swap entry when
the swap wasn't initialized yet. I would just drop the BUG_ON and bail
out when the slot cache hasn't been initialized yet.
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: kernel BUG at mm/swap_slots.c:270
@ 2017-03-19 14:04 ` Michal Hocko
0 siblings, 0 replies; 8+ messages in thread
From: Michal Hocko @ 2017-03-19 14:04 UTC (permalink / raw)
To: Linus Torvalds
Cc: Tim Chen, Huang, Ying, Andrew Morton, linux-mm,
Linux Kernel Mailing List
On Sat 18-03-17 09:57:18, Linus Torvalds wrote:
> Tim at al,
> I got this on my desktop at shutdown:
>
> ------------[ cut here ]------------
> kernel BUG at mm/swap_slots.c:270!
> invalid opcode: 0000 [#1] SMP
> CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
> Hardware name: System manufacturer System Product Name/Z170-K, BIOS
> 1803 05/06/2016
> RIP: 0010:free_swap_slot+0xba/0xd0
> Call Trace:
> swap_free+0x36/0x40
> do_swap_page+0x360/0x6d0
> __handle_mm_fault+0x880/0x1080
> handle_mm_fault+0xd0/0x240
> __do_page_fault+0x232/0x4d0
> do_page_fault+0x20/0x70
> page_fault+0x22/0x30
> ---[ end trace aefc9ede53e0ab21 ]---
>
> so there seems to be something screwy in the new swap_slots code.
I am travelling (LSFMM) so I didn't get to look at this more thoroughly
but it seems like a race because enable_swap_slots_cache is called at
the very end of the swapon and we could have already created a swap
entry for a page by that time I guess.
> Any ideas? I'm not finding other reports of this, but I'm also not
> seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
> much checks whether swap_slot_cache_initialized has been set, so the
> BUG_ON() just seems like garbage. But please take a look.
I guess you are right. I cannot speak of the original intention but it
seems Tim wanted to be careful to not see unexpected swap entry when
the swap wasn't initialized yet. I would just drop the BUG_ON and bail
out when the slot cache hasn't been initialized yet.
--
Michal Hocko
SUSE Labs
--
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: kernel BUG at mm/swap_slots.c:270
2017-03-19 14:04 ` Michal Hocko
@ 2017-03-20 1:25 ` Huang, Ying
-1 siblings, 0 replies; 8+ messages in thread
From: Huang, Ying @ 2017-03-20 1:25 UTC (permalink / raw)
To: Michal Hocko, Linus Torvalds
Cc: Tim Chen, Huang, Ying, Andrew Morton, linux-mm,
Linux Kernel Mailing List
Hi,
Michal Hocko <mhocko@kernel.org> writes:
> On Sat 18-03-17 09:57:18, Linus Torvalds wrote:
>> Tim at al,
>> I got this on my desktop at shutdown:
>>
>> ------------[ cut here ]------------
>> kernel BUG at mm/swap_slots.c:270!
>> invalid opcode: 0000 [#1] SMP
>> CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
>> Hardware name: System manufacturer System Product Name/Z170-K, BIOS
>> 1803 05/06/2016
>> RIP: 0010:free_swap_slot+0xba/0xd0
>> Call Trace:
>> swap_free+0x36/0x40
>> do_swap_page+0x360/0x6d0
>> __handle_mm_fault+0x880/0x1080
>> handle_mm_fault+0xd0/0x240
>> __do_page_fault+0x232/0x4d0
>> do_page_fault+0x20/0x70
>> page_fault+0x22/0x30
>> ---[ end trace aefc9ede53e0ab21 ]---
>>
>> so there seems to be something screwy in the new swap_slots code.
>
> I am travelling (LSFMM) so I didn't get to look at this more thoroughly
> but it seems like a race because enable_swap_slots_cache is called at
> the very end of the swapon and we could have already created a swap
> entry for a page by that time I guess.
>
>> Any ideas? I'm not finding other reports of this, but I'm also not
>> seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
>> much checks whether swap_slot_cache_initialized has been set, so the
>> BUG_ON() just seems like garbage. But please take a look.
>
> I guess you are right. I cannot speak of the original intention but it
> seems Tim wanted to be careful to not see unexpected swap entry when
> the swap wasn't initialized yet. I would just drop the BUG_ON and bail
> out when the slot cache hasn't been initialized yet.
Yes. The BUG_ON() is problematic. The initialization of swap slot
cache may fail too, if so, we should still allow using swap without slot
cache. Will send out a fixing patch ASAP.
Best Regards,
Huang, Ying
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: kernel BUG at mm/swap_slots.c:270
@ 2017-03-20 1:25 ` Huang, Ying
0 siblings, 0 replies; 8+ messages in thread
From: Huang, Ying @ 2017-03-20 1:25 UTC (permalink / raw)
To: Michal Hocko, Linus Torvalds
Cc: Tim Chen, Huang, Ying, Andrew Morton, linux-mm,
Linux Kernel Mailing List
Hi,
Michal Hocko <mhocko@kernel.org> writes:
> On Sat 18-03-17 09:57:18, Linus Torvalds wrote:
>> Tim at al,
>> I got this on my desktop at shutdown:
>>
>> ------------[ cut here ]------------
>> kernel BUG at mm/swap_slots.c:270!
>> invalid opcode: 0000 [#1] SMP
>> CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
>> Hardware name: System manufacturer System Product Name/Z170-K, BIOS
>> 1803 05/06/2016
>> RIP: 0010:free_swap_slot+0xba/0xd0
>> Call Trace:
>> swap_free+0x36/0x40
>> do_swap_page+0x360/0x6d0
>> __handle_mm_fault+0x880/0x1080
>> handle_mm_fault+0xd0/0x240
>> __do_page_fault+0x232/0x4d0
>> do_page_fault+0x20/0x70
>> page_fault+0x22/0x30
>> ---[ end trace aefc9ede53e0ab21 ]---
>>
>> so there seems to be something screwy in the new swap_slots code.
>
> I am travelling (LSFMM) so I didn't get to look at this more thoroughly
> but it seems like a race because enable_swap_slots_cache is called at
> the very end of the swapon and we could have already created a swap
> entry for a page by that time I guess.
>
>> Any ideas? I'm not finding other reports of this, but I'm also not
>> seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
>> much checks whether swap_slot_cache_initialized has been set, so the
>> BUG_ON() just seems like garbage. But please take a look.
>
> I guess you are right. I cannot speak of the original intention but it
> seems Tim wanted to be careful to not see unexpected swap entry when
> the swap wasn't initialized yet. I would just drop the BUG_ON and bail
> out when the slot cache hasn't been initialized yet.
Yes. The BUG_ON() is problematic. The initialization of swap slot
cache may fail too, if so, we should still allow using swap without slot
cache. Will send out a fixing patch ASAP.
Best Regards,
Huang, Ying
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: kernel BUG at mm/swap_slots.c:270
2017-03-20 1:25 ` Huang, Ying
@ 2017-03-20 14:15 ` Tim Chen
-1 siblings, 0 replies; 8+ messages in thread
From: Tim Chen @ 2017-03-20 14:15 UTC (permalink / raw)
To: Huang, Ying
Cc: Michal Hocko, Linus Torvalds, Andrew Morton, linux-mm,
Linux Kernel Mailing List
On Mon, Mar 20, 2017 at 09:25:50AM +0800, Huang, Ying wrote:
> Hi,
>
> Michal Hocko <mhocko@kernel.org> writes:
>
> > On Sat 18-03-17 09:57:18, Linus Torvalds wrote:
> >> Tim at al,
> >> I got this on my desktop at shutdown:
> >>
> >> ------------[ cut here ]------------
> >> kernel BUG at mm/swap_slots.c:270!
> >> invalid opcode: 0000 [#1] SMP
> >> CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
> >> Hardware name: System manufacturer System Product Name/Z170-K, BIOS
> >> 1803 05/06/2016
> >> RIP: 0010:free_swap_slot+0xba/0xd0
> >> Call Trace:
> >> swap_free+0x36/0x40
> >> do_swap_page+0x360/0x6d0
> >> __handle_mm_fault+0x880/0x1080
> >> handle_mm_fault+0xd0/0x240
> >> __do_page_fault+0x232/0x4d0
> >> do_page_fault+0x20/0x70
> >> page_fault+0x22/0x30
> >> ---[ end trace aefc9ede53e0ab21 ]---
> >>
> >> so there seems to be something screwy in the new swap_slots code.
> >
> > I am travelling (LSFMM) so I didn't get to look at this more thoroughly
> > but it seems like a race because enable_swap_slots_cache is called at
> > the very end of the swapon and we could have already created a swap
> > entry for a page by that time I guess.
> >
> >> Any ideas? I'm not finding other reports of this, but I'm also not
> >> seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
> >> much checks whether swap_slot_cache_initialized has been set, so the
> >> BUG_ON() just seems like garbage. But please take a look.
> >
> > I guess you are right. I cannot speak of the original intention but it
> > seems Tim wanted to be careful to not see unexpected swap entry when
> > the swap wasn't initialized yet. I would just drop the BUG_ON and bail
> > out when the slot cache hasn't been initialized yet.
>
> Yes. The BUG_ON() is problematic. The initialization of swap slot
> cache may fail too, if so, we should still allow using swap without slot
> cache. Will send out a fixing patch ASAP.
>
I kind of suspect that the swap slot cache initialization failed for some
reason. But swap should still work when we try to free a swap slot
without the slots cache.
A proposed patch to fix this problem:
--->8---
From: Tim Chen <tim.c.chen@linux.intel.com>
Date: Mon, 20 Mar 2017 10:00:03 -0400
Subject: [PATCH] mm/swap: Fix inappropriate BUG_ON in swap_slots.c
It is possible that we don't have swap_slots cache configured and
running when swap is in use and swap slot is freed. So the BUG_ON is
in appropriate when swap_slots cache is not initizliaed when a swap slot
is released.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
mm/swap_slots.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/swap_slots.c b/mm/swap_slots.c
index 9b5bc86..a17ecbf 100644
--- a/mm/swap_slots.c
+++ b/mm/swap_slots.c
@@ -267,10 +267,11 @@ int free_swap_slot(swp_entry_t entry)
{
struct swap_slots_cache *cache;
- BUG_ON(!swap_slot_cache_initialized);
+ if (unlikely(!use_swap_slot_cache))
+ swapcache_free_entries(&entry, 1);
cache = &get_cpu_var(swp_slots);
- if (use_swap_slot_cache && cache->slots_ret) {
+ if (cache->slots_ret) {
spin_lock_irq(&cache->free_lock);
/* Swap slots cache may be deactivated before acquiring lock */
if (!use_swap_slot_cache) {
--
2.5.5
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: kernel BUG at mm/swap_slots.c:270
@ 2017-03-20 14:15 ` Tim Chen
0 siblings, 0 replies; 8+ messages in thread
From: Tim Chen @ 2017-03-20 14:15 UTC (permalink / raw)
To: Huang, Ying
Cc: Michal Hocko, Linus Torvalds, Andrew Morton, linux-mm,
Linux Kernel Mailing List
On Mon, Mar 20, 2017 at 09:25:50AM +0800, Huang, Ying wrote:
> Hi,
>
> Michal Hocko <mhocko@kernel.org> writes:
>
> > On Sat 18-03-17 09:57:18, Linus Torvalds wrote:
> >> Tim at al,
> >> I got this on my desktop at shutdown:
> >>
> >> ------------[ cut here ]------------
> >> kernel BUG at mm/swap_slots.c:270!
> >> invalid opcode: 0000 [#1] SMP
> >> CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
> >> Hardware name: System manufacturer System Product Name/Z170-K, BIOS
> >> 1803 05/06/2016
> >> RIP: 0010:free_swap_slot+0xba/0xd0
> >> Call Trace:
> >> swap_free+0x36/0x40
> >> do_swap_page+0x360/0x6d0
> >> __handle_mm_fault+0x880/0x1080
> >> handle_mm_fault+0xd0/0x240
> >> __do_page_fault+0x232/0x4d0
> >> do_page_fault+0x20/0x70
> >> page_fault+0x22/0x30
> >> ---[ end trace aefc9ede53e0ab21 ]---
> >>
> >> so there seems to be something screwy in the new swap_slots code.
> >
> > I am travelling (LSFMM) so I didn't get to look at this more thoroughly
> > but it seems like a race because enable_swap_slots_cache is called at
> > the very end of the swapon and we could have already created a swap
> > entry for a page by that time I guess.
> >
> >> Any ideas? I'm not finding other reports of this, but I'm also not
> >> seeing why it should BUG_ON(). The "use_swap_slot_cache" thing very
> >> much checks whether swap_slot_cache_initialized has been set, so the
> >> BUG_ON() just seems like garbage. But please take a look.
> >
> > I guess you are right. I cannot speak of the original intention but it
> > seems Tim wanted to be careful to not see unexpected swap entry when
> > the swap wasn't initialized yet. I would just drop the BUG_ON and bail
> > out when the slot cache hasn't been initialized yet.
>
> Yes. The BUG_ON() is problematic. The initialization of swap slot
> cache may fail too, if so, we should still allow using swap without slot
> cache. Will send out a fixing patch ASAP.
>
I kind of suspect that the swap slot cache initialization failed for some
reason. But swap should still work when we try to free a swap slot
without the slots cache.
A proposed patch to fix this problem:
--->8---
From: Tim Chen <tim.c.chen@linux.intel.com>
Date: Mon, 20 Mar 2017 10:00:03 -0400
Subject: [PATCH] mm/swap: Fix inappropriate BUG_ON in swap_slots.c
It is possible that we don't have swap_slots cache configured and
running when swap is in use and swap slot is freed. So the BUG_ON is
in appropriate when swap_slots cache is not initizliaed when a swap slot
is released.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
mm/swap_slots.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/swap_slots.c b/mm/swap_slots.c
index 9b5bc86..a17ecbf 100644
--- a/mm/swap_slots.c
+++ b/mm/swap_slots.c
@@ -267,10 +267,11 @@ int free_swap_slot(swp_entry_t entry)
{
struct swap_slots_cache *cache;
- BUG_ON(!swap_slot_cache_initialized);
+ if (unlikely(!use_swap_slot_cache))
+ swapcache_free_entries(&entry, 1);
cache = &get_cpu_var(swp_slots);
- if (use_swap_slot_cache && cache->slots_ret) {
+ if (cache->slots_ret) {
spin_lock_irq(&cache->free_lock);
/* Swap slots cache may be deactivated before acquiring lock */
if (!use_swap_slot_cache) {
--
2.5.5
--
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^ permalink raw reply related [flat|nested] 8+ messages in thread
end of thread, other threads:[~2017-03-20 14:20 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-03-18 16:57 kernel BUG at mm/swap_slots.c:270 Linus Torvalds
2017-03-18 16:57 ` Linus Torvalds
2017-03-19 14:04 ` Michal Hocko
2017-03-19 14:04 ` Michal Hocko
2017-03-20 1:25 ` Huang, Ying
2017-03-20 1:25 ` Huang, Ying
2017-03-20 14:15 ` Tim Chen
2017-03-20 14:15 ` Tim Chen
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