From: Peter Zijlstra <peterz@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Dmitry Vyukov <dvyukov@google.com>,
Clark Williams <williams@redhat.com>,
Alexander Potapenko <glider@google.com>,
kasan-dev <kasan-dev@googlegroups.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-rt-users@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] mm/kasan: make quarantine_lock a raw_spinlock_t
Date: Sat, 13 Oct 2018 15:50:58 +0200 [thread overview]
Message-ID: <20181013135058.GC4931@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20181012165655.f067886428a394dc7fbae7af@linux-foundation.org>
On Fri, Oct 12, 2018 at 04:56:55PM -0700, Andrew Morton wrote:
> There are several reasons for using raw_*, so an explanatory comment at
> each site is called for.
>
> However it would be smarter to stop "using raw_* for several reasons".
> Instead, create a differently named variant for each such reason. ie, do
>
> /*
> * Nice comment goes here. It explains all the possible reasons why -rt
> * might use a raw_spin_lock when a spin_lock could otherwise be used.
> */
> #define raw_spin_lock_for_rt raw_spinlock
>
> Then use raw_spin_lock_for_rt() at all such sites.
The whole raw_spinlock_t is for RT, no other reason. It is the one true
spinlock.
From this, it naturally follows that:
- nesting order: raw_spinlock_t < spinlock_t < mutex_t
- raw_spinlock_t sections must be bounded
The patch under discussion is the result of the nesting order rule; and
is allowed to violate the second rule, by virtue of it being debug code.
There are no other reasons; and I'm somewhat confused by what you
propose.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Dmitry Vyukov <dvyukov@google.com>,
Clark Williams <williams@redhat.com>,
Alexander Potapenko <glider@google.com>,
kasan-dev <kasan-dev@googlegroups.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-rt-users@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] mm/kasan: make quarantine_lock a raw_spinlock_t
Date: Sat, 13 Oct 2018 15:50:58 +0200 [thread overview]
Message-ID: <20181013135058.GC4931@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20181012165655.f067886428a394dc7fbae7af@linux-foundation.org>
On Fri, Oct 12, 2018 at 04:56:55PM -0700, Andrew Morton wrote:
> There are several reasons for using raw_*, so an explanatory comment at
> each site is called for.
>
> However it would be smarter to stop "using raw_* for several reasons".
> Instead, create a differently named variant for each such reason. ie, do
>
> /*
> * Nice comment goes here. It explains all the possible reasons why -rt
> * might use a raw_spin_lock when a spin_lock could otherwise be used.
> */
> #define raw_spin_lock_for_rt raw_spinlock
>
> Then use raw_spin_lock_for_rt() at all such sites.
The whole raw_spinlock_t is for RT, no other reason. It is the one true
spinlock.
>From this, it naturally follows that:
- nesting order: raw_spinlock_t < spinlock_t < mutex_t
- raw_spinlock_t sections must be bounded
The patch under discussion is the result of the nesting order rule; and
is allowed to violate the second rule, by virtue of it being debug code.
There are no other reasons; and I'm somewhat confused by what you
propose.
next prev parent reply other threads:[~2018-10-13 13:51 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-18 15:29 [PATCH RT] rt: convert mm/kasan/quarantine_lock to raw_spinlock Clark Williams
2018-09-18 20:34 ` kbuild test robot
2018-10-05 16:37 ` Sebastian Andrzej Siewior
2018-10-18 9:04 ` [kbuild-all] " Rong Chen
2018-10-05 16:30 ` [PATCH] kasan: convert kasan/quarantine_lock " Sebastian Andrzej Siewior
2018-10-05 16:33 ` Sebastian Andrzej Siewior
2018-10-08 0:47 ` Clark Williams
2018-10-08 9:15 ` Dmitry Vyukov
2018-10-09 14:27 ` Sebastian Andrzej Siewior
2018-10-10 8:25 ` Dmitry Vyukov
2018-10-10 9:29 ` Sebastian Andrzej Siewior
2018-10-10 9:45 ` Dmitry Vyukov
2018-10-10 9:53 ` Sebastian Andrzej Siewior
2018-10-10 9:57 ` Dmitry Vyukov
2018-10-10 21:49 ` [PATCH] mm/kasan: make quarantine_lock a raw_spinlock_t Sebastian Andrzej Siewior
2018-10-11 8:03 ` Dmitry Vyukov
2018-10-12 23:56 ` Andrew Morton
2018-10-13 13:50 ` Peter Zijlstra [this message]
2018-10-13 13:50 ` Peter Zijlstra
2018-10-15 23:35 ` Andrew Morton
2018-10-19 10:58 ` Peter Zijlstra
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