linux-kernel - Re: [RFC v8 PATCH 2/5] uprobes: introduce has

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Date:   Thu, 23 Aug 2018 17:15:55 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Yang Shi <yang.shi@...ux.alibaba.com>, mhocko@...nel.org,
        willy@...radead.org, ldufour@...ux.vnet.ibm.com,
        kirill@...temov.name, akpm@...ux-foundation.org,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-mm@...ck.org, liu.song.a23@...il.com,
        ravi.bangoria@...ux.ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC v8 PATCH 2/5] uprobes: introduce has_uprobes helper

On 08/22, Srikar Dronamraju wrote:
>
> * Vlastimil Babka <vbabka@...e.cz> [2018-08-22 12:55:59]:
>
> > On 08/15/2018 08:49 PM, Yang Shi wrote:
> > > We need check if mm or vma has uprobes in the following patch to check
> > > if a vma could be unmapped with holding read mmap_sem.

Confused... why can't we call uprobe_munmap() under read_lock(mmap_sem) ?

OK, it can race with find_active_uprobe() but I do not see anything really
wrong, and a false-positive MMF_RECALC_UPROBES is fine.

Again, I think we should simply kill uprobe_munmap(), but this needs another
discussion.

Oleg.