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Date:   Mon, 9 Apr 2018 15:29:28 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc:     mhiramat@kernel.org, peterz@infradead.org,
        srikar@linux.vnet.ibm.com, rostedt@goodmis.org, acme@kernel.org,
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        kstewart@linuxfoundation.org, linux-doc@vger.kernel.org,
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        naveen.n.rao@linux.vnet.ibm.com, pc@us.ibm.com, tglx@linutronix.de,
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Subject: Re: [PATCH v2 7/9] trace_uprobe/sdt: Fix multiple update of same
 reference counter
Message-ID: <20180409132928.GA25722@redhat.com>
References: <20180404083110.18647-1-ravi.bangoria@linux.vnet.ibm.com>
 <20180404083110.18647-8-ravi.bangoria@linux.vnet.ibm.com>
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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, but let me repeat that
I didn't read this version yet.

Oleg.