All of lore.kernel.org
 help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: Jann Horn <jannh@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Darren Hart <dvhart@infradead.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] threads: Update PID limit comment according to futex UAPI change
Date: Tue, 3 Mar 2020 11:25:40 +0100	[thread overview]
Message-ID: <20200303102540.GC2579@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200302112939.8068-1-jannh@google.com>

On Mon, Mar 02, 2020 at 12:29:39PM +0100, Jann Horn wrote:
> The futex UAPI changed back in commit 76b81e2b0e22 ("[PATCH] lightweight
> robust futexes updates 2"), which landed in v2.6.17: FUTEX_TID_MASK is now
> 0x3fffffff instead of 0x1fffffff. Update the corresponding comment in
> include/linux/threads.h.
> 
> Signed-off-by: Jann Horn <jannh@google.com>
> ---
>  include/linux/threads.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/threads.h b/include/linux/threads.h
> index 3086dba525e20..18d5a74bcc3dd 100644
> --- a/include/linux/threads.h
> +++ b/include/linux/threads.h
> @@ -29,7 +29,7 @@
>  
>  /*
>   * A maximum of 4 million PIDs should be enough for a while.
> - * [NOTE: PID/TIDs are limited to 2^29 ~= 500+ million, see futex.h.]
> + * [NOTE: PID/TIDs are limited to 2^30 ~= 1 billion, see FUTEX_TID_MASK.]
>   */
>  #define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \
>  	(sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT))

I just noticed another mention of this in Documentation/robust-futex-ABI.txt
There it states that bit-29 is reserved for future use.

Thomas, do we want to release that bit and update all this?

  reply	other threads:[~2020-03-03 10:25 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-02 11:29 [PATCH] threads: Update PID limit comment according to futex UAPI change Jann Horn
2020-03-03 10:25 ` Peter Zijlstra [this message]
2020-03-03 14:12   ` Thomas Gleixner
2023-05-11 12:47     ` Thomas Gleixner
2023-05-11 13:26       ` Thomas Gleixner
2020-03-21 16:50 ` [tip: sched/core] " tip-bot2 for Jann Horn

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=20200303102540.GC2579@hirez.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=akpm@linux-foundation.org \
    --cc=dvhart@infradead.org \
    --cc=jannh@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=tglx@linutronix.de \
    /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.