Patch "kthread: fix boot hang (regression) on MIPS/OpenRISC" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

kthread: fix boot hang (regression) on MIPS/OpenRISC

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kthread-fix-boot-hang-regression-on-mips-openrisc.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Vegard Nossum <[email protected]>
Date: Mon, 29 May 2017 09:22:07 +0200
Subject: kthread: fix boot hang (regression) on MIPS/OpenRISC

From: Vegard Nossum <[email protected]>

commit b0f5a8f32e8bbdaae1abb8abe2d3cbafaba57e08 upstream.

This fixes a regression in commit 4d6501dce079 where I didn't notice that MIPS and OpenRISC were reinitialising p->{set,clear}_child_tid to NULL after our initialisation in copy_process().

We can simply get rid of the arch-specific initialisation here since it is now always done in copy_process() before hitting copy_thread{,_tls}().

Review notes:

- As far as I can tell, copy_process() is the only user of copy_thread_tls(), which is the only caller of copy_thread() for architectures that don't implement copy_thread_tls().

- After this patch, there is no arch-specific code touching p->set_child_tid or p->clear_child_tid whatsoever.

- It may look like MIPS/OpenRISC wanted to always have these fields be NULL, but that's not true, as copy_process() would unconditionally set them again _after_ calling copy_thread_tls() before commit 4d6501dce079.

---
 arch/mips/kernel/process.c     |    1 -
 arch/openrisc/kernel/process.c |    2 --
 2 files changed, 3 deletions(-)

@@ -120,7 +120,6 @@ int copy_thread(unsigned long clone_flag
 	struct thread_info *ti = task_thread_info(p);
 	struct pt_regs *childregs, *regs = current_pt_regs();
 	unsigned long childksp;
-	p->set_child_tid = p->clear_child_tid = NULL;
 
 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 

@@ -167,8 +167,6 @@ copy_thread(unsigned long clone_flags, u
 
 	top_of_kernel_stack = sp;
 
-	p->set_child_tid = p->clear_child_tid = NULL;
-
 	/* Locate userspace context on stack... */
 	sp -= STACK_FRAME_OVERHEAD;	/* redzone */
 	sp -= sizeof(struct pt_regs);

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/kthread-fix-boot-hang-regression-on-mips-openrisc.patch queue-4.11/kthread-fix-use-after-free-if-kthread-fork-fails.patch