linux-kernel - Re: [PATCH v6 06/33] riscv/Kconfig: enable HAVE_EXIT

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Message-ID: <ZyFcVSMh2hJ+wAAa@debug.ba.rivosinc.com>
Date: Tue, 29 Oct 2024 15:06:13 -0700
From: Deepak Gupta <debug@...osinc.com>
To: Mark Brown <broonie@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
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	Andrew Morton <akpm@...ux-foundation.org>,
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Subject: Re: [PATCH v6 06/33] riscv/Kconfig: enable HAVE_EXIT_THREAD for riscv

On Wed, Oct 09, 2024 at 12:28:03PM +0100, Mark Brown wrote:
>On Tue, Oct 08, 2024 at 03:36:48PM -0700, Deepak Gupta wrote:
>
>> riscv will need an implementation for exit_thread to clean up shadow stack
>> when thread exits. If current thread had shadow stack enabled, shadow
>> stack is allocated by default for any new thread.
>
>FWIW both arm64 and x86 do this via deactivate_mm().  ISTR there's some
>case where exit_thread() doesn't quite do the right thing but I can't
>remember the specifics right now, possibly the vfork() case but ICBW?
>In any case like Rick said factoring out the common patterns would be
>good, keeping things aligned would support that.

Now getting back to collecting feedback and sending another version.
Yeah I found what you meant.
https://lore.kernel.org/all/20230908203655.543765-1-rick.p.edgecombe@intel.com/#t

Seems like an issue for riscv as well. Will fix it.
This particular issue screaming out loud for converging flows as well.