linux-kernel - Re: [PATCH v11 09/14] entry: Rework syscall_exit_to_user_mode

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Message-ID: <3bfa15fc-187e-4c39-9cb3-a936fdd443b2@arm.com>
Date: Thu, 29 Jan 2026 17:00:14 +0100
From: Kevin Brodsky <kevin.brodsky@....com>
To: Jinjie Ruan <ruanjinjie@...wei.com>, catalin.marinas@....com,
 will@...nel.org, oleg@...hat.com, tglx@...utronix.de, peterz@...radead.org,
 luto@...nel.org, shuah@...nel.org, kees@...nel.org, wad@...omium.org,
 deller@....de, akpm@...ux-foundation.org, charlie@...osinc.com,
 mark.rutland@....com, anshuman.khandual@....com, song@...nel.org,
 ryan.roberts@....com, thuth@...hat.com, ada.coupriediaz@....com,
 broonie@...nel.org, pengcan@...inos.cn, liqiang01@...inos.cn, kmal@...k.li,
 dvyukov@...gle.com, reddybalavignesh9979@...il.com,
 richard.weiyang@...il.com, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v11 09/14] entry: Rework syscall_exit_to_user_mode_work()
 for arch reuse

On 29/01/2026 14:11, Jinjie Ruan wrote:
>>> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
>>> index e4a8287af822..c4fea642d931 100644
>>> --- a/include/linux/entry-common.h
>>> +++ b/include/linux/entry-common.h
>>> @@ -125,14 +125,14 @@ void syscall_exit_work(struct pt_regs *regs, unsigned long work);
>>>   * syscall_exit_to_user_mode_work - Handle work before returning to user mode
>>>   * @regs:	Pointer to currents pt_regs
>>>   *
>>> - * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
>>> + * Same as step 1 of syscall_exit_to_user_mode() but without calling
>>> + * local_irq_disable(), syscall_exit_to_user_mode_prepare() and
>>>   * exit_to_user_mode() to perform the final transition to user mode.
>>>   *
>>> - * Calling convention is the same as for syscall_exit_to_user_mode() and it
>>> - * returns with all work handled and interrupts disabled. The caller must
>>> - * invoke exit_to_user_mode() before actually switching to user mode to
>>> - * make the final state transitions. Interrupts must stay disabled between
>>> - * return from this function and the invocation of exit_to_user_mode().
>>> + * Calling convention is the same as for syscall_exit_to_user_mode(). The
>>> + * caller must invoke local_irq_disable(), __exit_to_user_mode_prepare() and
>> Shouldn't it be syscall_exit_to_user_mode_prepare() rather than
>> __exit_to_user_mode_prepare()? The former has extra calls (e.g. rseq).
> Perhaps we can just delete these comments — at present only generic
> entry and arm64 use it, and nowhere else needs it; after the refactoring
> the comments now seem rather unclear.

Agreed, the comments are essentially describing what each function
calls; considering how short they are, directly reading the code is
probably easier.

- Kevin