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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: Pavel Machek <pavel@ucw.cz>, carlos <carlos@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	libc-alpha <libc-alpha@sourceware.org>
Subject: Re: Restartable Sequences system call merged into Linux
Date: Thu, 14 Jun 2018 09:46:46 -0400 (EDT)	[thread overview]
Message-ID: <1399480624.13011.1528984006717.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <1110f198-88c2-544d-6836-f901b8e90f98@redhat.com>

----- On Jun 14, 2018, at 9:32 AM, Florian Weimer fweimer@redhat.com wrote:

> On 06/14/2018 03:25 PM, Pavel Machek wrote:
> 
>> But the proposal wanted to add a syscall to thread creation, right?
>> And I believe that may be noticeable.
> 
> We already call set_robust_list, so we could just pass a larger area to
> that and the kernel could use it.  Then no additional system call would
> be needed in the common case (new kernel which recognizes the new area
> size).
> 
> But then we cannot use an initial-exec thread local variable for it
> (although the offset from the thread pointer will still be constant, of
> course).

I'm wondering whether we could turn the problem around: expose a new
system call allowing to register an array of pointers to per-thread data,
which would be used rather than set_robust_list when available. This way,
we could register both the robust list and rseq with a single system call,
e.g.:

enum linux_tls_area_type {
    LINUX_TLS_ROBUST_LIST,
    LINUX_TLS_RSEQ,
};

struct linux_tls_area_item {
    enum linux_tls_area_type type;
    void *p;
};

long sys_register_tls_areas(struct linux_tls_area_item *array, size_t nb)

This would allow registering various TLS data structures with a single
system call without hindering flexibility on the user-space side. For
instance, we could still use initial-exec and the __rseq_abi symbol for
rseq with this approach.

Thoughts ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

  reply	other threads:[~2018-06-14 13:46 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-11 19:49 Mathieu Desnoyers
2018-06-11 19:55 ` Florian Weimer
2018-06-11 20:04   ` Mathieu Desnoyers
2018-06-12 13:11     ` Florian Weimer
2018-06-12 16:31       ` Mathieu Desnoyers
2018-06-13  8:21         ` Florian Weimer
2018-06-14 12:27         ` Pavel Machek
2018-06-14 13:01           ` Mathieu Desnoyers
2018-06-14 13:25             ` Pavel Machek
2018-06-14 13:32               ` Florian Weimer
2018-06-14 13:46                 ` Mathieu Desnoyers [this message]
2018-06-15  5:10                   ` Florian Weimer
2018-06-15 17:44                     ` Mathieu Desnoyers
2018-06-14 13:38               ` Mathieu Desnoyers
2018-06-14 13:49                 ` Pavel Machek
2018-06-14 14:00                   ` Florian Weimer
2018-06-14 14:36                     ` Mathieu Desnoyers
2018-06-14 14:41                       ` Florian Weimer
2018-06-14 15:09                         ` Mathieu Desnoyers
2018-06-15  5:09             ` Florian Weimer
2018-06-15 17:50               ` Mathieu Desnoyers
2018-06-15  5:07           ` Florian Weimer
2018-06-13 11:48 ` Heiko Carstens
2018-06-13 16:14   ` Mathieu Desnoyers
2018-06-13 19:53     ` Mathieu Desnoyers

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