From: Thomas Gleixner <[email protected]>
The handle_exit_race() function is defined in commit c158b461306df82
("futex: Cure exit race"), which never returns -EBUSY. This results
in a small piece of dead code in the attach_to_pi_owner() function:
int ret = handle_exit_race(uaddr, uval, p); /* Never return -EBUSY */
...
if (ret == -EBUSY)
*exiting = p; /* dead code */
The return value -EBUSY is added to handle_exit_race() in upsteam
commit ac31c7ff8624409 ("futex: Provide distinct return value when
owner is exiting"). This commit was incorporated into v4.9.255, before
the function handle_exit_race() was introduced, whitout Modify
handle_exit_race().
To fix dead code, extract the change of handle_exit_race() from
commit ac31c7ff8624409 ("futex: Provide distinct return value when owner
is exiting"), re-incorporated.
Fixes: c158b461306df82 ("futex: Cure exit race")
Cc: [email protected] # 4.9.258-rc1
Signed-off-by: Xiaoming Ni <[email protected]>
---
kernel/futex.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index b65dbb5d60bb..0fd785410150 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1207,11 +1207,11 @@ static int handle_exit_race(u32 __user *uaddr, u32 uval,
u32 uval2;
/*
- * If the futex exit state is not yet FUTEX_STATE_DEAD, wait
- * for it to finish.
+ * If the futex exit state is not yet FUTEX_STATE_DEAD, tell the
+ * caller that the alleged owner is busy.
*/
if (tsk && tsk->futex_state != FUTEX_STATE_DEAD)
- return -EAGAIN;
+ return -EBUSY;
/*
* Reread the user space value to handle the following situation:
--
2.27.0
On Mon, Feb 22, 2021 at 08:53:52PM +0800, Xiaoming Ni wrote:
> From: Thomas Gleixner <[email protected]>
>
> The handle_exit_race() function is defined in commit c158b461306df82
> ("futex: Cure exit race"), which never returns -EBUSY. This results
> in a small piece of dead code in the attach_to_pi_owner() function:
>
> int ret = handle_exit_race(uaddr, uval, p); /* Never return -EBUSY */
> ...
> if (ret == -EBUSY)
> *exiting = p; /* dead code */
>
> The return value -EBUSY is added to handle_exit_race() in upsteam
> commit ac31c7ff8624409 ("futex: Provide distinct return value when
> owner is exiting"). This commit was incorporated into v4.9.255, before
> the function handle_exit_race() was introduced, whitout Modify
> handle_exit_race().
>
> To fix dead code, extract the change of handle_exit_race() from
> commit ac31c7ff8624409 ("futex: Provide distinct return value when owner
> is exiting"), re-incorporated.
>
> Fixes: c158b461306df82 ("futex: Cure exit race")
> Cc: [email protected] # 4.9.258-rc1
> Signed-off-by: Xiaoming Ni <[email protected]>
> ---
> kernel/futex.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
What is the git commit id of this patch in Linus's tree?
Also, what kernel tree(s) is this supposed to go to?
thanks,
greg k-h
On 2021/2/25 16:25, Greg KH wrote:
> On Mon, Feb 22, 2021 at 08:53:52PM +0800, Xiaoming Ni wrote:
>> From: Thomas Gleixner <[email protected]>
>>
>> The handle_exit_race() function is defined in commit c158b461306df82
>> ("futex: Cure exit race"), which never returns -EBUSY. This results
>> in a small piece of dead code in the attach_to_pi_owner() function:
>>
>> int ret = handle_exit_race(uaddr, uval, p); /* Never return -EBUSY */
>> ...
>> if (ret == -EBUSY)
>> *exiting = p; /* dead code */
>>
>> The return value -EBUSY is added to handle_exit_race() in upsteam
>> commit ac31c7ff8624409 ("futex: Provide distinct return value when
>> owner is exiting"). This commit was incorporated into v4.9.255, before
>> the function handle_exit_race() was introduced, whitout Modify
>> handle_exit_race().
>>
>> To fix dead code, extract the change of handle_exit_race() from
>> commit ac31c7ff8624409 ("futex: Provide distinct return value when owner
>> is exiting"), re-incorporated.
mainline:
ac31c7ff8624 futex: Provide distinct return value when owner is exiting
>>
>> Fixes: c158b461306df82 ("futex: Cure exit race")
stable linux-4.9.y
9c3f39860367 futex: Cure exit race
c27f392040e2 futex: Provide distinct return value when owner is exiting
>> Cc: [email protected] # 4.9.258-rc1
>> Signed-off-by: Xiaoming Ni <[email protected]>
>> ---
>> kernel/futex.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> What is the git commit id of this patch in Linus's tree?
>
> Also, what kernel tree(s) is this supposed to go to?
>
> thanks,
>
> greg k-h
> .
>
Sorry, the commit id c158b461306df82 in the patch does not exist in the
linux-stable repository.
The commit ID is from linux-stable-rc.
I corrected the commit id in a subsequent email, and added a branch
label.
https://lore.kernel.org/lkml/[email protected]/
Sorry, I forgot to use "--in-reply-to=" when I sent the update patch.
This issue occurs only in the linux-4.9.y branch v4.9.258
Thanks
xiaoming Ni
On Thu, 25 Feb 2021, Xiaoming Ni wrote:
> On 2021/2/25 16:25, Greg KH wrote:
> > On Mon, Feb 22, 2021 at 08:53:52PM +0800, Xiaoming Ni wrote:
> > > From: Thomas Gleixner <[email protected]>
> > >
> > > The handle_exit_race() function is defined in commit c158b461306df82
> > > ("futex: Cure exit race"), which never returns -EBUSY. This results
> > > in a small piece of dead code in the attach_to_pi_owner() function:
> > >
> > > int ret = handle_exit_race(uaddr, uval, p); /* Never return -EBUSY */
> > > ...
> > > if (ret == -EBUSY)
> > > *exiting = p; /* dead code */
> > >
> > > The return value -EBUSY is added to handle_exit_race() in upsteam
> > > commit ac31c7ff8624409 ("futex: Provide distinct return value when
> > > owner is exiting"). This commit was incorporated into v4.9.255, before
> > > the function handle_exit_race() was introduced, whitout Modify
> > > handle_exit_race().
> > >
> > > To fix dead code, extract the change of handle_exit_race() from
> > > commit ac31c7ff8624409 ("futex: Provide distinct return value when owner
> > > is exiting"), re-incorporated.
> mainline:
> ac31c7ff8624 futex: Provide distinct return value when owner is exiting
>
> > >
> > > Fixes: c158b461306df82 ("futex: Cure exit race")
>
> stable linux-4.9.y
> 9c3f39860367 futex: Cure exit race
> c27f392040e2 futex: Provide distinct return value when owner is exiting
>
> > > Cc: [email protected] # 4.9.258-rc1
> > > Signed-off-by: Xiaoming Ni <[email protected]>
> > > ---
> > > kernel/futex.c | 6 +++---
> > > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > What is the git commit id of this patch in Linus's tree?
> >
> > Also, what kernel tree(s) is this supposed to go to?
> >
> > thanks,
> >
> > greg k-h
> > .
> >
> Sorry, the commit id c158b461306df82 in the patch does not exist in the
> linux-stable repository.
> The commit ID is from linux-stable-rc.
>
> I corrected the commit id in a subsequent email, and added a branch label.
> https://lore.kernel.org/lkml/[email protected]/
Replied to the follow-up.
> Sorry, I forgot to use "--in-reply-to=" when I sent the update patch.
>
> This issue occurs only in the linux-4.9.y branch v4.9.258
--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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