Re: [PATCH 4.4 3/3] futex: fix dead code in attach_to_pi_owner()
From: Zhengyejian (Zetta)
Date: Wed Mar 10 2021 - 20:40:30 EST
On 2021/3/10 22:10, Greg KH wrote:
On Wed, Mar 10, 2021 at 01:28:02PM +0000, Lee Jones wrote:
On Wed, 10 Mar 2021, Greg KH wrote:
On Tue, Mar 09, 2021 at 06:14:37PM +0000, Lee Jones wrote:
On Tue, 09 Mar 2021, Greg KH wrote:
On Tue, Mar 09, 2021 at 11:06:05AM +0800, Zheng Yejian wrote:
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
The handle_exit_race() function is defined in commit 9c3f39860367
("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.
Lee writes:
This commit takes the remaining functional snippet of:
ac31c7ff8624409 ("futex: Provide distinct return value when owner is exiting")
... and is the correct fix for this issue.
Fixes: 9c3f39860367 ("futex: Cure exit race")
Cc: stable@xxxxxxxxxxxxxxx # v4.9.258
Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
Reviewed-by: Lee Jones <lee.jones@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
---
kernel/futex.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
Same here, what is the upstream git id?
It doesn't have one as such - it's a part-patch:
This commit takes the remaining functional snippet of:
ac31c7ff8624409 ("futex: Provide distinct return value when owner is exiting")
That wasn't obvious :(
This was also my thinking, which is why I replied to the original
patch in an attempt to clarify what I thought was happening.
Is this a backport of another patch in the stable tree somewhere?
Yes, it looks like it.
The full patch was back-ported to v4.14 as:
e6e00df182908f34360c3c9f2d13cc719362e9c0
Ok, Zheng, can you put this information in the patch and resend the
whole series?
Sure, I'll send a "v2" patchset soon.
Thanks for your suggestions,
Zheng Yejian