From: Linus Torvalds <torvalds@linux-foundation.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Galbraith <efault@gmx.de>, Oleg Nesterov <oleg@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 03/10] sched/headers: Make task_struct::wake_q an opaque pointer
Date: Wed, 8 Feb 2017 12:00:40 -0800 [thread overview]
Message-ID: <CA+55aFy2er_QwhherSPMuzPSMhTtDPjW3m0NYxC2j1-FhWJ-AA@mail.gmail.com> (raw)
In-Reply-To: <1486578863-8903-4-git-send-email-mingo@kernel.org>
On Wed, Feb 8, 2017 at 10:34 AM, Ingo Molnar <mingo@kernel.org> wrote:
> To be able to decouple wake_q functionality from <linux/sched.h> make
> the basic task_struct::wake_q pointer an opaque void *.
Please don't use "void *" for opaque pointers.
You lose all typechecking, and this is just complete garbage:
+ struct wake_q_node *node = (void *)&task->wake_q;
What? You're casting a "void *" to "void *"? WTF?
The proper way to do opaque pointers is to declare them as pointers to
a structure that hasn't been defined (ie use a "struct xyz;" forward
declaration), and then that structure is only actually defined in the
places that use the otherwise opaque pointer.
That way you
(a) never need to cast anything
(b) get proper (and strong) type checking for the pointers.
and the people who need to look into it automatically do the right
thing, while anybody else who tries to dereference or otherwise use
the struct pointer will get a compiler error.
Linus
next prev parent reply other threads:[~2017-02-08 20:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-08 18:34 [PATCH 00/10] sched.h modernization -v2, phase #1: "Pre-splitup cleanups" Ingo Molnar
2017-02-08 18:34 ` [PATCH 01/10] sched/headers: Make all include/linux/sched/*.h headers build standalone Ingo Molnar
2017-02-08 18:34 ` [PATCH 02/10] sched/core: Convert ___assert_task_state() link time assert to BUILD_BUG_ON() Ingo Molnar
2017-02-08 18:34 ` [PATCH 03/10] sched/headers: Make task_struct::wake_q an opaque pointer Ingo Molnar
2017-02-08 20:00 ` Linus Torvalds [this message]
2017-02-08 21:37 ` [PATCH] sched/wake_q: Restore task_struct::wake_q type safety Ingo Molnar
2017-02-08 18:34 ` [PATCH 04/10] sched/core: Move the get_preempt_disable_ip() inline to sched/core.c Ingo Molnar
2017-02-08 18:34 ` [PATCH 05/10] sched/core: Remove the tsk_cpus_allowed() wrapper Ingo Molnar
2017-02-09 8:53 ` Peter Zijlstra
2017-02-09 9:08 ` Ingo Molnar
2017-02-09 11:46 ` Thomas Gleixner
2017-02-09 20:28 ` Ingo Molnar
2017-02-08 18:34 ` [PATCH 06/10] sched/core: Remove the tsk_nr_cpus_allowed() wrapper Ingo Molnar
2017-02-08 18:34 ` [PATCH 07/10] rcu: Separate the RCU synchronization types and APIs into <linux/rcupdate_wait.h> Ingo Molnar
2017-02-11 19:17 ` Paul McKenney
2017-02-08 18:34 ` [PATCH 08/10] sched/headers, cgroups: Remove the threadgroup_change_*() wrappery Ingo Molnar
2017-02-08 18:34 ` [PATCH 09/10] mm/vmacache, sched/headers: Introduce 'struct vmacache' and move it from <linux/sched.h> to <linux/mm_types> Ingo Molnar
2017-02-08 18:34 ` [PATCH 10/10] kasan, sched/headers: Uninline kasan_enable/disable_current() Ingo Molnar
2017-02-08 20:23 ` [PATCH 00/10] sched.h modernization -v2, phase #1: "Pre-splitup cleanups" Linus Torvalds
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