Re: [PATCH] arm: add support for TIF_NOTIFY_SIGNAL

[Jens Axboe <axboe@kernel.dk>]

On 11/12/20 8:32 AM, Russell King - ARM Linux admin wrote:
> On Tue, Nov 03, 2020 at 08:11:49AM -0700, Jens Axboe wrote:
>> On 10/29/20 11:42 AM, Russell King - ARM Linux admin wrote:
>>> On Thu, Oct 29, 2020 at 11:20:07AM -0600, Jens Axboe wrote:
>>>> On 10/29/20 11:17 AM, Russell King - ARM Linux admin wrote:
>>>>> On Thu, Oct 29, 2020 at 11:15:37AM -0600, Jens Axboe wrote:
>>>>>> How about this?
>>>>>>
>>>>>> commit c03932936d8f99ff7c1c6c7d984e7a457284396c
>>>>>> Author: Jens Axboe <axboe@kernel.dk>
>>>>>> Date:   Fri Oct 9 16:00:49 2020 -0600
>>>>>>
>>>>>>     arm: add support for TIF_NOTIFY_SIGNAL
>>>>>>     
>>>>>>     Wire up TIF_NOTIFY_SIGNAL handling for arm.
>>>>>>     
>>>>>>     Cc: linux-arm-kernel@lists.infradead.org
>>>>>>     Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>>>>>
>>>>>> diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
>>>>>> index 536b6b979f63..eb7ce2747eb0 100644
>>>>>> --- a/arch/arm/include/asm/thread_info.h
>>>>>> +++ b/arch/arm/include/asm/thread_info.h
>>>>>> @@ -126,6 +126,8 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
>>>>>>   * thread information flags:
>>>>>>   *  TIF_USEDFPU		- FPU was used by this task this quantum (SMP)
>>>>>>   *  TIF_POLLING_NRFLAG	- true if poll_idle() is polling TIF_NEED_RESCHED
>>>>>> + *
>>>>>> + * Any bit in the range of 0..15 will cause do_work_pending() to be invoked.
>>>>>>   */
>>>>>>  #define TIF_SIGPENDING		0	/* signal pending */
>>>>>>  #define TIF_NEED_RESCHED	1	/* rescheduling necessary */
>>>>>> @@ -135,6 +137,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
>>>>>>  #define TIF_SYSCALL_AUDIT	5	/* syscall auditing active */
>>>>>>  #define TIF_SYSCALL_TRACEPOINT	6	/* syscall tracepoint instrumentation */
>>>>>>  #define TIF_SECCOMP		7	/* seccomp syscall filtering active */
>>>>>> +#define TIF_NOTIFY_SIGNAL	8	/* signal notifications exist */
>>>>>>  
>>>>>>  #define TIF_USING_IWMMXT	17
>>>>>>  #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
>>>>>> @@ -148,6 +151,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
>>>>>>  #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
>>>>>>  #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
>>>>>>  #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
>>>>>> +#define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
>>>>>>  #define _TIF_USING_IWMMXT	(1 << TIF_USING_IWMMXT)
>>>>>>  
>>>>>>  /* Checks for any syscall work in entry-common.S */
>>>>>> @@ -158,7 +162,8 @@ extern int vfp_restore_user_hwstate(struct user_vfp *,
>>>>>>   * Change these and you break ASM code in entry-common.S
>>>>>>   */
>>>>>>  #define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
>>>>>> -				 _TIF_NOTIFY_RESUME | _TIF_UPROBE)
>>>>>> +				 _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
>>>>>> +				 _TIF_NOTIFY_SIGNAL)
>>>>>>  
>>>>>>  #endif /* __KERNEL__ */
>>>>>>  #endif /* __ASM_ARM_THREAD_INFO_H */
>>>>>> diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
>>>>>> index 271cb8a1eba1..77d16390a524 100644
>>>>>> --- a/arch/arm/kernel/entry-common.S
>>>>>> +++ b/arch/arm/kernel/entry-common.S
>>>>>> @@ -53,7 +53,7 @@ __ret_fast_syscall:
>>>>>>  	cmp	r2, #TASK_SIZE
>>>>>>  	blne	addr_limit_check_failed
>>>>>>  	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
>>>>>> -	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
>>>>>> +	movs	r1, r1, lsl #16
>>>>>>  	bne	fast_work_pending
>>>>>>  
>>>>>>  
>>>>>> @@ -90,7 +90,7 @@ __ret_fast_syscall:
>>>>>>  	cmp	r2, #TASK_SIZE
>>>>>>  	blne	addr_limit_check_failed
>>>>>>  	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
>>>>>> -	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
>>>>>> +	movs	r1, r1, lsl #16
>>>>>>  	beq	no_work_pending
>>>>>>   UNWIND(.fnend		)
>>>>>>  ENDPROC(ret_fast_syscall)
>>>>>> @@ -131,7 +131,7 @@ ENTRY(ret_to_user_from_irq)
>>>>>>  	cmp	r2, #TASK_SIZE
>>>>>>  	blne	addr_limit_check_failed
>>>>>>  	ldr	r1, [tsk, #TI_FLAGS]
>>>>>> -	tst	r1, #_TIF_WORK_MASK
>>>>>> +	movs	r1, r1, lsl #16
>>>>>>  	bne	slow_work_pending
>>>>>>  no_work_pending:
>>>>>>  	asm_trace_hardirqs_on save = 0
>>>>>> diff --git a/arch/arm/kernel/entry-v7m.S b/arch/arm/kernel/entry-v7m.S
>>>>>> index de1f20624be1..d0e898608d30 100644
>>>>>> --- a/arch/arm/kernel/entry-v7m.S
>>>>>> +++ b/arch/arm/kernel/entry-v7m.S
>>>>>> @@ -59,7 +59,7 @@ __irq_entry:
>>>>>>  
>>>>>>  	get_thread_info tsk
>>>>>>  	ldr	r2, [tsk, #TI_FLAGS]
>>>>>> -	tst	r2, #_TIF_WORK_MASK
>>>>>> +	movs	r2, r2, lsl #16
>>>>>>  	beq	2f			@ no work pending
>>>>>>  	mov	r0, #V7M_SCB_ICSR_PENDSVSET
>>>>>>  	str	r0, [r1, V7M_SCB_ICSR]	@ raise PendSV
>>>>>> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
>>>>>> index 585edbfccf6d..9d2e916121be 100644
>>>>>> --- a/arch/arm/kernel/signal.c
>>>>>> +++ b/arch/arm/kernel/signal.c
>>>>>> @@ -655,7 +655,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
>>>>>>  			if (unlikely(!user_mode(regs)))
>>>>>>  				return 0;
>>>>>>  			local_irq_enable();
>>>>>> -			if (thread_flags & _TIF_SIGPENDING) {
>>>>>> +			if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
>>>>>>  				int restart = do_signal(regs, syscall);
>>>>>>  				if (unlikely(restart)) {
>>>>>>  					/*
>>>>>>
>>>>>
>>>>> Looks perfect to me, thanks! I assume the pre-requisits for this are
>>>>> already in mainline or linux-next?
>>>>
>>>> Great! Thanks for your expedient attention and help.
>>>>
>>>> The bits using this are queued in tip for 5.11, so not in mainline yet,
>>>> but should be in linux-next tomorrow I guess. But it was done such that
>>>> arch patches could be queued up independently, so we didn't have weird
>>>> cross dependencies.
>>>
>>> Okay, I'll wait a few days and see about temporarily dumping it in
>>> my for-next branch so it gets a spin through kernelci next week.
>>> I'm not anticipating any breakage, so (if I remember) I'll give you
>>> a reviewed-by next week once it seems good. As I say, if I remember.
>>
>> Russell, did you have a chance to run it through the machinery?
> 
> I threw the patch on top of my for-next branch, and let the various
> autobuilders chew on it for a few days. I haven't had any reports
> back, not even of any breakage through me adding it to my tree.
> 
> I guess that's a positive indication.

Good enough to add your acked-by?

-- 
Jens Axboe


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