This patch is for stable branch linux-4.4-y.
On 2019/6/12 9:54, ZhangXiaoxu wrote:
The upstram commit 65d8fc777f6d ("futex: Remove requirement for lock_page() in get_futex_key()") use variable 'page' as the page head, when merge it to stable branch, the variable `page_head` is page head.
In the stable branch, the variable `page` not means the page head, when lock the page head, we should lock 'page_head', rather than 'page'.
It maybe lead a hung task problem.
Signed-off-by: ZhangXiaoxu zhangxiaoxu5@huawei.com Cc: stable@vger.kernel.org
kernel/futex.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c index ec9df5b..15d850f 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -593,8 +593,8 @@ again: * applies. If this is really a shmem page then the page lock * will prevent unexpected transitions. */
lock_page(page);shmem_swizzled = PageSwapCache(page) || page->mapping;
lock_page(page_head);shmem_swizzled = PageSwapCache(page_head) || page_head->mapping;
On Wed, Jun 12, 2019 at 09:50:25AM +0800, zhangxiaoxu (A) wrote:
This patch is for stable branch linux-4.4-y.
On 2019/6/12 9:54, ZhangXiaoxu wrote:
The upstram commit 65d8fc777f6d ("futex: Remove requirement for lock_page() in get_futex_key()") use variable 'page' as the page head, when merge it to stable branch, the variable `page_head` is page head.
In the stable branch, the variable `page` not means the page head, when lock the page head, we should lock 'page_head', rather than 'page'.
It maybe lead a hung task problem.
Signed-off-by: ZhangXiaoxu zhangxiaoxu5@huawei.com Cc: stable@vger.kernel.org
kernel/futex.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
I do not understand.
Please read https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to submit a patch to the stable trees properly.
If the commit is not in Linus's tree, then we can not take it, unless something is _very_ broken and it is the only way it can be resolved.
thanks,
greg k-h
On Wed, 12 Jun 2019, Greg KH wrote:
On Wed, Jun 12, 2019 at 09:50:25AM +0800, zhangxiaoxu (A) wrote:
This patch is for stable branch linux-4.4-y.
On 2019/6/12 9:54, ZhangXiaoxu wrote:
The upstram commit 65d8fc777f6d ("futex: Remove requirement for lock_page() in get_futex_key()") use variable 'page' as the page head, when merge it to stable branch, the variable `page_head` is page head.
In the stable branch, the variable `page` not means the page head, when lock the page head, we should lock 'page_head', rather than 'page'.
It maybe lead a hung task problem.
Signed-off-by: ZhangXiaoxu zhangxiaoxu5@huawei.com Cc: stable@vger.kernel.org
kernel/futex.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
I do not understand.
Please read https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to submit a patch to the stable trees properly.
If the commit is not in Linus's tree, then we can not take it, unless something is _very_ broken and it is the only way it can be resolved.
There is something _very_ broken. Upstream is correct but the 4.4. backport of the above commit is broken (93dcb09e29bb24a86aa7b7eff65e424f7dc98af2) in the way Zhang described. So it's a 4.4. only issue.
Thanks,
tglx
On Wed, Jun 12, 2019 at 09:29:48AM +0200, Thomas Gleixner wrote:
On Wed, 12 Jun 2019, Greg KH wrote:
On Wed, Jun 12, 2019 at 09:50:25AM +0800, zhangxiaoxu (A) wrote:
This patch is for stable branch linux-4.4-y.
On 2019/6/12 9:54, ZhangXiaoxu wrote:
The upstram commit 65d8fc777f6d ("futex: Remove requirement for lock_page() in get_futex_key()") use variable 'page' as the page head, when merge it to stable branch, the variable `page_head` is page head.
In the stable branch, the variable `page` not means the page head, when lock the page head, we should lock 'page_head', rather than 'page'.
It maybe lead a hung task problem.
Signed-off-by: ZhangXiaoxu zhangxiaoxu5@huawei.com Cc: stable@vger.kernel.org
kernel/futex.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
I do not understand.
Please read https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to submit a patch to the stable trees properly.
If the commit is not in Linus's tree, then we can not take it, unless something is _very_ broken and it is the only way it can be resolved.
There is something _very_ broken. Upstream is correct but the 4.4. backport of the above commit is broken (93dcb09e29bb24a86aa7b7eff65e424f7dc98af2) in the way Zhang described. So it's a 4.4. only issue.
That wasn't obvious at all, and wasn't cc:ed to stable to start with...
Anyway, I'll go queue this up to the 4.4.y tree if no one objects...
thanks,
greg k-h
linux-stable-mirror@lists.linaro.org
-
Greg KH -
Thomas Gleixner -
zhangxiaoxu (A)