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From:   Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Subject: Re: [PATCH v2 7/9] trace_uprobe/sdt: Fix multiple update of same
 reference counter
To:     Oleg Nesterov <oleg@redhat.com>
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        Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
References: <20180404083110.18647-1-ravi.bangoria@linux.vnet.ibm.com>
 <20180404083110.18647-8-ravi.bangoria@linux.vnet.ibm.com>
 <20180409132928.GA25722@redhat.com>
Date:   Tue, 10 Apr 2018 13:49:12 +0530
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Hi Oleg,

On 04/09/2018 06:59 PM, Oleg Nesterov wrote:
> On 04/04, Ravi Bangoria wrote:
>> +static void sdt_add_mm_list(struct trace_uprobe *tu, struct mm_struct *mm)
>> +{
>> +	struct mmu_notifier *mn;
>> +	struct sdt_mm_list *sml = kzalloc(sizeof(*sml), GFP_KERNEL);
>> +
>> +	if (!sml)
>> +		return;
>> +	sml->mm = mm;
>> +	list_add(&(sml->list), &(tu->sml.list));
>> +
>> +	/* Register mmu_notifier for this mm. */
>> +	mn = kzalloc(sizeof(*mn), GFP_KERNEL);
>> +	if (!mn)
>> +		return;
>> +
>> +	mn->ops = &sdt_mmu_notifier_ops;
>> +	__mmu_notifier_register(mn, mm);
>> +}
> and what if __mmu_notifier_register() fails simply because signal_pending() == T?
> see mm_take_all_locks().
>
> at first glance this all look suspicious and sub-optimal,

Yes. I should have added checks for failure cases.
Will fix them in v3.

Thanks for the review,
Ravi

>  but let me repeat that
> I didn't read this version yet.
>
> Oleg.
>