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From: Nicholas Piggin <npiggin@gmail.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Christophe Leroy <christophe.leroy@c-s.fr>,
	Michael Ellerman <mpe@ellerman.id.au>,
	msuchanek@suse.de, Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 13/13] powerpc/kernel: Do not use READ_ONCE() to access current thread_info flags
Date: Mon, 06 Apr 2020 11:39:19 +1000	[thread overview]
Message-ID: <1586137083.v4cw2k5x9e.astroid@bobo.none> (raw)
In-Reply-To: <3b9257ea1f3e107b81437671fa9d3942e31c6735.1586108649.git.christophe.leroy@c-s.fr>

Christophe Leroy's on April 6, 2020 3:44 am:
> current is a volatile pointer hold by r2 register.
> 
> READ_ONCE() is not required.
> 
> Before: 327 cycles on null_syscall
> Before: 325 cycles on null_syscall

Patches against Michael's next-test branch have a few small changes 
here. I need to look at the fallout on 64-bit code, although most
likely it's not measurable so if it saves you a few cycles we can
lean toward what ppc32 prefers.

Same with the compat test.

Thanks,
Nick

  reply	other threads:[~2020-04-06  1:42 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-05 17:44 [RFC PATCH v2 01/13] powerpc/radix: Make kuap_check_amr() and kuap_restore_amr() generic Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 02/13] powerpc/32s: Create C version of kuap_restore() and kuap_check() Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 03/13] powerpc/8xx: " Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 04/13] powerpc/irq: Add new helpers to play with MSR_EE and MSR_RI on PPC32 Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 05/13] powerpc/syscall: Rename syscall_64.c into syscall.c Christophe Leroy
2020-04-06  1:42   ` Nicholas Piggin
2020-04-06 18:20     ` Christophe Leroy
2020-04-07  0:22       ` Nicholas Piggin
2020-04-05 17:44 ` [RFC PATCH v2 06/13] powerpc/syscall: Make syscall_64.c buildable on PPC32 Christophe Leroy
2020-04-06  1:52   ` Nicholas Piggin
2020-04-06 18:21     ` Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 07/13] powerpc/syscall: Use is_compat_task() Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 08/13] powerpc/syscall: Save r3 in regs->orig_r3 Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 09/13] powerpc/syscall: Selectively check MSR_RI and MSR_PR on syscall entry Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 10/13] powerpc/syscall: system call implement entry/exit logic in C for PPC32 Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 11/13] powerpc/syscall: Avoid stack frame in likely part of syscall_call_exception() Christophe Leroy
2020-04-06  1:29   ` Nicholas Piggin
2020-04-06 18:19     ` Christophe Leroy
2020-04-05 17:44 ` [RFC PATCH v2 12/13] powerpc/kernel: Do not inconditionally save non volatile registers on system call Christophe Leroy
2020-04-06  1:25   ` Nicholas Piggin
2020-04-06 18:18     ` Christophe Leroy
2020-04-07  0:26       ` Nicholas Piggin
2020-04-05 17:44 ` [RFC PATCH v2 13/13] powerpc/kernel: Do not use READ_ONCE() to access current thread_info flags Christophe Leroy
2020-04-06  1:39   ` Nicholas Piggin [this message]
2020-04-06  1:40 ` [RFC PATCH v2 01/13] powerpc/radix: Make kuap_check_amr() and kuap_restore_amr() generic Nicholas Piggin

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