All of lore.kernel.org
 help / color / mirror / Atom feed
From: Palmer Dabbelt <palmer@dabbelt.com>
To: parri.andrea@gmail.com
Cc: mathieu.desnoyers@efficios.com, paulmck@kernel.org,
	Paul Walmsley <paul.walmsley@sifive.com>,
	aou@eecs.berkeley.edu, mmaas@google.com, hboehm@google.com,
	striker@us.ibm.com, charlie@rivosinc.com, rehn@rivosinc.com,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] membarrier: riscv: Provide core serializing command
Date: Wed, 06 Dec 2023 05:05:48 -0800 (PST)	[thread overview]
Message-ID: <mhng-40f43849-e610-410b-92b5-7571838ce9f5@palmer-ri-x1c9> (raw)
In-Reply-To: <ZWe+ljzCUQQVu7oD@andrea>

On Wed, 29 Nov 2023 14:43:34 PST (-0800), parri.andrea@gmail.com wrote:
>> > So I should probably stick to 93917ad50972, which apparently selected
>> > CONFIG_MEMBARRIER on RISC-V, for the Fixes: tag in question.
>>
>> I think it goes further than that, because you can explicitly
>> CONFIG_MEMBARRIER=y, see init/Kconfig:
>>
>> config MEMBARRIER
>>         bool "Enable membarrier() system call" if EXPERT
>>         default y
>>         help
>>           Enable the membarrier() system call that allows issuing memory
>>           barriers across all running threads, which can be used to distribute
>>           the cost of user-space memory barriers asymmetrically by transforming
>>           pairs of memory barriers into pairs consisting of membarrier() and a
>>           compiler barrier.
>>
>>           If unsure, say Y.
>>
>> Before 1464d00b27b2, riscv just happened to set it to =n in the defconfig.
>>
>> I suspect the initial port of riscv merged after v4.14 was already broken.
>
> I see.  Oh well, guess I'll have to leave this up to the maintainers then
> (I believe I've never managed to build riscv that far), Palmer?

I see

$ git grep "config MEMBARRIER" fab957c11efe2f405e08b9f0d080524bc2631428
fab957c11efe2f405e08b9f0d080524bc2631428:init/Kconfig:config MEMBARRIER

so IMO this is just one of those forever bugs.  So I'd lean towards

    Fixes: fab957c11efe ("RISC-V: Atomic and Locking Code")

(or anything in that original patch set).  It's not that big of a 
backport, so I think it's safe enough?

>> > I'll look into adding the membarrier feature you mention (as a final/
>> > follow-up patch), unless you or someone else want to take care of it.
>>
>> I'll be happy to review it :)
>
> Sweet!  :-)
>
>   Andrea

WARNING: multiple messages have this Message-ID (diff)
From: Palmer Dabbelt <palmer@dabbelt.com>
To: parri.andrea@gmail.com
Cc: mathieu.desnoyers@efficios.com, paulmck@kernel.org,
	Paul Walmsley <paul.walmsley@sifive.com>,
	aou@eecs.berkeley.edu, mmaas@google.com, hboehm@google.com,
	striker@us.ibm.com, charlie@rivosinc.com, rehn@rivosinc.com,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] membarrier: riscv: Provide core serializing command
Date: Wed, 06 Dec 2023 05:05:48 -0800 (PST)	[thread overview]
Message-ID: <mhng-40f43849-e610-410b-92b5-7571838ce9f5@palmer-ri-x1c9> (raw)
In-Reply-To: <ZWe+ljzCUQQVu7oD@andrea>

On Wed, 29 Nov 2023 14:43:34 PST (-0800), parri.andrea@gmail.com wrote:
>> > So I should probably stick to 93917ad50972, which apparently selected
>> > CONFIG_MEMBARRIER on RISC-V, for the Fixes: tag in question.
>>
>> I think it goes further than that, because you can explicitly
>> CONFIG_MEMBARRIER=y, see init/Kconfig:
>>
>> config MEMBARRIER
>>         bool "Enable membarrier() system call" if EXPERT
>>         default y
>>         help
>>           Enable the membarrier() system call that allows issuing memory
>>           barriers across all running threads, which can be used to distribute
>>           the cost of user-space memory barriers asymmetrically by transforming
>>           pairs of memory barriers into pairs consisting of membarrier() and a
>>           compiler barrier.
>>
>>           If unsure, say Y.
>>
>> Before 1464d00b27b2, riscv just happened to set it to =n in the defconfig.
>>
>> I suspect the initial port of riscv merged after v4.14 was already broken.
>
> I see.  Oh well, guess I'll have to leave this up to the maintainers then
> (I believe I've never managed to build riscv that far), Palmer?

I see

$ git grep "config MEMBARRIER" fab957c11efe2f405e08b9f0d080524bc2631428
fab957c11efe2f405e08b9f0d080524bc2631428:init/Kconfig:config MEMBARRIER

so IMO this is just one of those forever bugs.  So I'd lean towards

    Fixes: fab957c11efe ("RISC-V: Atomic and Locking Code")

(or anything in that original patch set).  It's not that big of a 
backport, so I think it's safe enough?

>> > I'll look into adding the membarrier feature you mention (as a final/
>> > follow-up patch), unless you or someone else want to take care of it.
>>
>> I'll be happy to review it :)
>
> Sweet!  :-)
>
>   Andrea

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2023-12-06 13:05 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-27 10:32 [PATCH 0/2] membarrier: riscv: Provide core serializing command Andrea Parri
2023-11-27 10:32 ` Andrea Parri
2023-11-27 10:32 ` [PATCH 1/2] locking: Introduce prepare_sync_core_cmd() Andrea Parri
2023-11-27 10:32   ` Andrea Parri
2023-11-27 12:53   ` Mathieu Desnoyers
2023-11-27 12:53     ` Mathieu Desnoyers
2023-11-27 10:32 ` [PATCH 2/2] membarrier: riscv: Provide core serializing command Andrea Parri
2023-11-27 10:32   ` Andrea Parri
2023-11-27 13:28   ` Mathieu Desnoyers
2023-11-27 13:28     ` Mathieu Desnoyers
2023-11-28 15:13     ` Andrea Parri
2023-11-28 15:13       ` Andrea Parri
2023-11-28 18:39       ` Mathieu Desnoyers
2023-11-28 18:39         ` Mathieu Desnoyers
2023-11-29 18:29         ` Andrea Parri
2023-11-29 18:29           ` Andrea Parri
2023-11-29 20:00           ` Mathieu Desnoyers
2023-11-29 20:00             ` Mathieu Desnoyers
2023-11-29 21:25             ` Andrea Parri
2023-11-29 21:25               ` Andrea Parri
2023-11-29 21:32               ` Mathieu Desnoyers
2023-11-29 21:32                 ` Mathieu Desnoyers
2023-11-29 22:43                 ` Andrea Parri
2023-11-29 22:43                   ` Andrea Parri
2023-12-06 13:05                   ` Palmer Dabbelt [this message]
2023-12-06 13:05                     ` Palmer Dabbelt
2023-12-06 14:11                     ` Andrea Parri
2023-12-06 14:11                       ` Andrea Parri
2023-12-06 14:15                       ` Palmer Dabbelt
2023-12-06 14:15                         ` Palmer Dabbelt
2023-12-06 17:42                         ` Andrea Parri
2023-12-06 17:42                           ` Andrea Parri
2023-12-06 17:56                           ` Palmer Dabbelt
2023-12-06 17:56                             ` Palmer Dabbelt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=mhng-40f43849-e610-410b-92b5-7571838ce9f5@palmer-ri-x1c9 \
    --to=palmer@dabbelt.com \
    --cc=aou@eecs.berkeley.edu \
    --cc=charlie@rivosinc.com \
    --cc=hboehm@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-riscv@lists.infradead.org \
    --cc=mathieu.desnoyers@efficios.com \
    --cc=mmaas@google.com \
    --cc=parri.andrea@gmail.com \
    --cc=paul.walmsley@sifive.com \
    --cc=paulmck@kernel.org \
    --cc=rehn@rivosinc.com \
    --cc=striker@us.ibm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.