From: Charan Teja Kalla <quic_charante@quicinc.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>, <surenb@google.com>,
<vbabka@suse.cz>, <rientjes@google.com>, <sfr@canb.auug.org.au>,
<edgararriaga@google.com>, <nadav.amit@gmail.com>,
<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
"# 5 . 10+" <stable@vger.kernel.org>
Subject: Re: [PATCH V2,2/2] mm: madvise: skip unmapped vma holes passed to process_madvise
Date: Tue, 22 Mar 2022 10:49:56 +0530 [thread overview]
Message-ID: <72b4183b-2ec7-dc73-0c21-b12f342860d4@quicinc.com> (raw)
In-Reply-To: <YjiTn+7vw2rXA6K/@dhcp22.suse.cz>
On 3/21/2022 8:32 PM, Michal Hocko wrote:
>> It can return EINTR when:
>> -------------------------
>> 1) PTRACE_MODE_READ is being checked in mm_access() where it is waiting
>> on task->signal->exec_update_lock. EINTR returned from here guarantees
>> that process_madvise() didn't event start processing.
>> https://elixir.bootlin.com/linux/v5.16.14/source/mm/madvise.c#L1264 -->
>> https://elixir.bootlin.com/linux/v5.16.14/source/kernel/fork.c#L1318
>>
>> 2) The process_madvise() started processing VMA's but the required
>> behavior on a VMA needs mmap_write_lock_killable(), from where EINTR is
>> returned.
> Please note this will happen if the task has been killed. The return
> value doesn't really matter because the process won't run in userspace.
Okay, thanks here.
>
>> The current behaviours supported by process_madvise(),
>> MADV_COLD, PAGEOUT, WILLNEED, just need read lock here.
>> https://elixir.bootlin.com/linux/v5.16.14/source/mm/madvise.c#L1164
>> **Thus I think no way for EINTR can be returned by process_madvise() in
>> the middle of processing.** . No?
> Maybe not with the current implementation but I can easily imagine that
> there is a requirement to break out early when there is a signal pending
> (e.g. to support terminating madvise on a large memory rage). You would
> get EINTR then somehow need to communicate that to the userspace.
Agree. Will implement this.
next prev parent reply other threads:[~2022-03-22 5:20 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-11 15:29 [PATCH V2,0/2]mm: madvise: return correct bytes processed with process_madvise Charan Teja Kalla
2022-03-11 15:29 ` [PATCH V2,1/2] mm: madvise: return correct bytes advised " Charan Teja Kalla
2022-03-15 22:20 ` Minchan Kim
2022-03-21 15:18 ` Michal Hocko
2022-03-11 15:29 ` [PATCH V2,2/2] mm: madvise: skip unmapped vma holes passed to process_madvise Charan Teja Kalla
2022-03-15 22:58 ` Minchan Kim
2022-03-15 23:48 ` Andrew Morton
2022-03-16 1:43 ` Minchan Kim
2022-03-16 14:19 ` Charan Teja Kalla
2022-03-16 21:29 ` Andrew Morton
2022-03-17 16:28 ` Minchan Kim
2022-03-17 16:53 ` Suren Baghdasaryan
2022-03-17 20:38 ` Nadav Amit
2022-03-18 14:05 ` Charan Teja Kalla
2022-03-18 15:37 ` Minchan Kim
2022-03-17 16:24 ` Minchan Kim
2022-03-21 15:02 ` Michal Hocko
2022-03-22 5:19 ` Charan Teja Kalla [this message]
2022-03-21 15:34 ` Michal Hocko
2022-03-22 7:10 ` Charan Teja Kalla
2022-03-22 8:40 ` Michal Hocko
2022-03-11 21:42 ` [PATCH V2,0/2]mm: madvise: return correct bytes processed with process_madvise Andrew Morton
2022-03-15 14:26 ` Charan Teja Kalla
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