From: Peter Zijlstra <peterz@infradead.org>
To: Peter Oskolkov <posk@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
linux-kernel@vger.kernel.org, Paul Turner <pjt@google.com>,
Chris Kennelly <ckennelly@google.com>,
Peter Oskolkov <posk@posk.io>
Subject: Re: [PATCH 1/2 v3] rseq/membarrier: add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ
Date: Tue, 11 Aug 2020 09:54:20 +0200 [thread overview]
Message-ID: <20200811075420.GA5637@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20200811062733.GP3982@worktop.programming.kicks-ass.net>
On Tue, Aug 11, 2020 at 08:27:33AM +0200, Peter Zijlstra wrote:
> SYSCALL_DEFINE2(membarrier, int, cmd, int, flags)
> {
> + int cflags = 0, int cpuid = -1;
> +
> if (unlikely(flags) && cmd != MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ)
> return -EINVAL;
> +
> + if (cmd & (MEMBARRIER_CMD_PRIVATE_EXPEDITED |
> + MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE |
> + MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ)) {
> +
> + if (cmd & MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ)
> + cflags |= MEMBARRIER_FLAG_RSEQ;
> +
> + if (cmd & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) {
> + cflags |= MEMBARRIER_FLAG_SYNC_CORE;
> + cpuid = flags;
> + }
> +
> + cmd = MEMBARRIER_CMD_PRIVATE_EXPEDITED;
> + }
This of course fails to check if other bits are set, and it goes really
'funny' if you use cpuid != -1.
That all needs a little more thought.
next prev parent reply other threads:[~2020-08-11 7:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-11 0:09 [PATCH 1/2 v3] rseq/membarrier: add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ Peter Oskolkov
2020-08-11 0:09 ` [PATCH 2/2 v3] rseq/selftests: test MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ Peter Oskolkov
2020-08-12 20:11 ` Mathieu Desnoyers
2020-08-11 6:27 ` [PATCH 1/2 v3] rseq/membarrier: add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ Peter Zijlstra
2020-08-11 7:54 ` Peter Zijlstra [this message]
2020-08-11 21:08 ` Peter Oskolkov
2020-08-12 18:30 ` Mathieu Desnoyers
2020-08-12 18:48 ` Peter Oskolkov
2020-08-12 19:44 ` Mathieu Desnoyers
2020-08-20 17:42 ` Peter Oskolkov
2020-08-25 16:58 ` Mathieu Desnoyers
2020-08-25 17:22 ` Peter Oskolkov
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