diff mbox series

[v5] mm,hwpoison: send SIGBUS to PF_MCE_EARLY processes on action required events

Message ID 20210120162422.0ed3dd56.yaoaili@kingsoft.com (mailing list archive)
State New
Headers show
Series [v5] mm,hwpoison: send SIGBUS to PF_MCE_EARLY processes on action required events | expand

Commit Message

Aili Yao Jan. 20, 2021, 8:24 a.m. UTC
When a memory uncorrected error is triggered by process who accessed
the address with error, It's Action Required Case for only current
process which triggered this; This Action Required case means Action
optional to other process who share the same page. Usually killing
current process will be sufficient, other processes sharing the same
page will get be signaled when they really touch the poisoned page.

But there is another scenario that other processes
sharing the same page want to be signaled early with PF_MCE_EARLY set,
In this case, we should get them into kill list and signal
BUS_MCEERR_AO to them.

So in this patch, task_early_kill will check current process if
force_early is set, and if not current,the code will fallback to
find_early_kill_thread() to check if there is PF_MCE_EARLY process
who cares the error.

In kill_proc(), BUS_MCEERR_AR is only send to current, other processes in
kill list will be signaled with BUS_MCEERR_AO.

Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Aili Yao <yaoaili@kingsoft.com>
---
 mm/memory-failure.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

Comments

Oscar Salvador Jan. 21, 2021, 10:03 a.m. UTC | #1
On Wed, Jan 20, 2021 at 04:24:22PM +0800, Aili Yao wrote:
> When a memory uncorrected error is triggered by process who accessed
> the address with error, It's Action Required Case for only current
> process which triggered this; This Action Required case means Action
> optional to other process who share the same page. Usually killing
> current process will be sufficient, other processes sharing the same
> page will get be signaled when they really touch the poisoned page.
> 
> But there is another scenario that other processes
> sharing the same page want to be signaled early with PF_MCE_EARLY set,
> In this case, we should get them into kill list and signal
> BUS_MCEERR_AO to them.
> 
> So in this patch, task_early_kill will check current process if
> force_early is set, and if not current,the code will fallback to
> find_early_kill_thread() to check if there is PF_MCE_EARLY process
> who cares the error.
> 
> In kill_proc(), BUS_MCEERR_AR is only send to current, other processes in
> kill list will be signaled with BUS_MCEERR_AO.
> 
> Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> Signed-off-by: Aili Yao <yaoaili@kingsoft.com>

Looks good to me, a few nits below.

Reviewed-by: Oscar Salvador <osalvador@suse.de>


> @@ -243,9 +243,12 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
>  			pfn, t->comm, t->pid);
>  
>  	if (flags & MF_ACTION_REQUIRED) {
> -		WARN_ON_ONCE(t != current);
> -		ret = force_sig_mceerr(BUS_MCEERR_AR,
> +		if (tk->tsk == current)
You can re-use "t" here.

> +			ret = force_sig_mceerr(BUS_MCEERR_AR,
>  					 (void __user *)tk->addr, addr_lsb);
> +		else
> +			ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
> +				addr_lsb, t);

I would place a brief comment above explaining why we are sending BUS_MCEER_AO
to non-current tasks.
E.g: "Signal other processes sharing the page if they have PF_MCE_EARLY set"

> @@ -457,8 +463,6 @@ static struct task_struct *task_early_kill(struct task_struct *tsk,
>  		 */
>  		if (tsk->mm == current->mm)
>  			return current;
> -		else
> -			return NULL;

 if (force_early && task->mm == current->mm)
         return current;
Aili Yao Jan. 22, 2021, 5:13 a.m. UTC | #2
On Thu, 21 Jan 2021 11:03:05 +0100
Oscar Salvador <osalvador@suse.de> wrote:

> On Wed, Jan 20, 2021 at 04:24:22PM +0800, Aili Yao wrote:
> > When a memory uncorrected error is triggered by process who accessed
> > the address with error, It's Action Required Case for only current
> > process which triggered this; This Action Required case means Action
> > optional to other process who share the same page. Usually killing
> > current process will be sufficient, other processes sharing the same
> > page will get be signaled when they really touch the poisoned page.
> > 
> > But there is another scenario that other processes
> > sharing the same page want to be signaled early with PF_MCE_EARLY set,
> > In this case, we should get them into kill list and signal
> > BUS_MCEERR_AO to them.
> > 
> > So in this patch, task_early_kill will check current process if
> > force_early is set, and if not current,the code will fallback to
> > find_early_kill_thread() to check if there is PF_MCE_EARLY process
> > who cares the error.
> > 
> > In kill_proc(), BUS_MCEERR_AR is only send to current, other processes in
> > kill list will be signaled with BUS_MCEERR_AO.
> > 
> > Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> > Signed-off-by: Aili Yao <yaoaili@kingsoft.com>  
> 
> Looks good to me, a few nits below.
> 
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> 
> 
> > @@ -243,9 +243,12 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
> >  			pfn, t->comm, t->pid);
> >  
> >  	if (flags & MF_ACTION_REQUIRED) {
> > -		WARN_ON_ONCE(t != current);
> > -		ret = force_sig_mceerr(BUS_MCEERR_AR,
> > +		if (tk->tsk == current)  
> You can re-use "t" here.

yeah, this look better, I will change to that. Thanks!

> 
> > +			ret = force_sig_mceerr(BUS_MCEERR_AR,
> >  					 (void __user *)tk->addr, addr_lsb);
> > +		else
> > +			ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
> > +				addr_lsb, t);  
> 
> I would place a brief comment above explaining why we are sending BUS_MCEER_AO
> to non-current tasks.
> E.g: "Signal other processes sharing the page if they have PF_MCE_EARLY set"

Yes, it's good to have

> 
> > @@ -457,8 +463,6 @@ static struct task_struct *task_early_kill(struct task_struct *tsk,
> >  		 */
> >  		if (tsk->mm == current->mm)
> >  			return current;
> > -		else
> > -			return NULL;  
> 
>  if (force_early && task->mm == current->mm)
>          return current;
>  
> 
This looks more cleaner.

I will modify above in a v6 patch!

Thanks,
diff mbox series

Patch

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5a38e9eade94..441fe2787cd4 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -243,9 +243,12 @@  static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
 			pfn, t->comm, t->pid);
 
 	if (flags & MF_ACTION_REQUIRED) {
-		WARN_ON_ONCE(t != current);
-		ret = force_sig_mceerr(BUS_MCEERR_AR,
+		if (tk->tsk == current)
+			ret = force_sig_mceerr(BUS_MCEERR_AR,
 					 (void __user *)tk->addr, addr_lsb);
+		else
+			ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
+				addr_lsb, t);
 	} else {
 		/*
 		 * Don't use force here, it's convenient if the signal
@@ -440,10 +443,13 @@  static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
  * Determine whether a given process is "early kill" process which expects
  * to be signaled when some page under the process is hwpoisoned.
  * Return task_struct of the dedicated thread (main thread unless explicitly
- * specified) if the process is "early kill," and otherwise returns NULL.
+ * specified) if the process is "early kill" and otherwise returns NULL.
  *
- * Note that the above is true for Action Optional case, but not for Action
- * Required case where SIGBUS should sent only to the current thread.
+ * Note that the above is true for Action Optional case. For Action Required
+ * case, it's only meaningful to the current thread which need to be signaled
+ * with SIGBUS, this error is Action Optional for other non current
+ * processes sharing the same error page,if the process is "early kill", the
+ * task_struct of the dedicated thread will also be returned.
  */
 static struct task_struct *task_early_kill(struct task_struct *tsk,
 					   int force_early)
@@ -457,8 +463,6 @@  static struct task_struct *task_early_kill(struct task_struct *tsk,
 		 */
 		if (tsk->mm == current->mm)
 			return current;
-		else
-			return NULL;
 	}
 	return find_early_kill_thread(tsk);
 }