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SubjectRe: [PATCH] mm, memory-failure: clarify error message
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Thanks Vishal and Naoya!

-jane

On 5/20/2019 3:21 AM, Naoya Horiguchi wrote:
> On Fri, May 17, 2019 at 10:18:02AM +0530, Anshuman Khandual wrote:
>>
>> On 05/17/2019 09:38 AM, Jane Chu wrote:
>>> Some user who install SIGBUS handler that does longjmp out
>> What the longjmp about ? Are you referring to the mechanism of catching the
>> signal which was registered ?
> AFAIK, longjmp() might be useful for signal-based retrying, so highly
> optimized applications like Oracle DB might want to utilize it to handle
> memory errors in application level, I guess.
>
>>> therefore keeping the process alive is confused by the error
>>> message
>>> "[188988.765862] Memory failure: 0x1840200: Killing
>>> cellsrv:33395 due to hardware memory corruption"
>> Its a valid point because those are two distinct actions.
>>
>>> Slightly modify the error message to improve clarity.
>>>
>>> Signed-off-by: Jane Chu <jane.chu@oracle.com>
>>> ---
>>> mm/memory-failure.c | 7 ++++---
>>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>>> index fc8b517..14de5e2 100644
>>> --- a/mm/memory-failure.c
>>> +++ b/mm/memory-failure.c
>>> @@ -216,10 +216,9 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
>>> short addr_lsb = tk->size_shift;
>>> int ret;
>>>
>>> - pr_err("Memory failure: %#lx: Killing %s:%d due to hardware memory corruption\n",
>>> - pfn, t->comm, t->pid);
>>> -
>>> if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
>>> + pr_err("Memory failure: %#lx: Killing %s:%d due to hardware memory "
>>> + "corruption\n", pfn, t->comm, t->pid);
>>> ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)tk->addr,
>>> addr_lsb, current);
>>> } else {
>>> @@ -229,6 +228,8 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
>>> * This could cause a loop when the user sets SIGBUS
>>> * to SIG_IGN, but hopefully no one will do that?
>>> */
>>> + pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware "
>>> + "memory corruption\n", pfn, t->comm, t->pid);
>>> ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
>>> addr_lsb, t); /* synchronous? */
>> As both the pr_err() messages are very similar, could not we just switch between "Killing"
>> and "Sending SIGBUS to" based on a variable e.g action_[kill|sigbus] evaluated previously
>> with ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm).
> That might need additional if sentence, which I'm not sure worth doing.
> I think that the simplest fix for the reported problem (a confusing message)
> is like below:
>
> - pr_err("Memory failure: %#lx: Killing %s:%d due to hardware memory corruption\n",
> + pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
> pfn, t->comm, t->pid);
>
> Or, if we have a good reason to separate the message for MF_ACTION_REQUIRED and
> MF_ACTION_OPTIONAL, that might be OK.
>
> Thanks,
> Naoya Horiguchi

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