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dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=goodmis.org header.i=@goodmis.org header.a=rsa-sha256 header.s=dkim1 header.b=vJDlW8Z5 Received: from omf07.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 04443160430; Wed, 21 Oct 2026 13:59:58 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf07.hostedemail.com (Postfix) with ESMTPA id C73FA2002C; Wed, 21 Oct 2026 13:59:56 +0000 (UTC) Date: Wed, 21 Oct 2026 09:59:55 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: John Stultz , Vincent Guittot , Christian Loehle , Qais Yousef , LKML , Hongyan Xia , Ingo Molnar , Wei Wang , Patrick Bellasi , Dietmar Eggemann Subject: Re: Uclamp races due to non-atomic static_branch_likely updates Message-ID: <20261021095955.0d06a754@gandalf.local.home> In-Reply-To: <20261021133430.GP2823843@noisy.programming.kicks-ass.net> References: <20261020152933.16989549@gandalf.local.home> <20261021113806.GE2823843@noisy.programming.kicks-ass.net> <20261021092136.249e2d19@gandalf.local.home> <20261021133430.GP2823843@noisy.programming.kicks-ass.net> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspamout06 X-Stat-Signature: ue6xqu4z8gfox4pzawfb61r3pfysas3m X-Rspamd-Queue-Id: C73FA2002C X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX183Q3TjqIpLggLVM1pINV6bZiqyyPvtDeY= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=goodmis.org; h=date:from:to:cc:subject:message-id:in-reply-to:references:mime-version:content-type:content-transfer-encoding; s=dkim1; bh=WXR6W2h/dyZK+RmqaIFVqYmeYGQdq0lkqTNQeZO+uao=; b=vJDlW8Z5lCC+qfvzev5BZ9c+GDZ4YkCPNIlocPgKnLr8/3Tz8bEw3pwpaqJLPgkXKVrzTIx1g0cHH5bAx4W/RmAGM/RPNtaNNrtJr2X6g3/GBgYM6Oh3yadHyRXN+H7iIIDa624aCX9bLxQEQH/wHkN9VvpzxdKi/o+qDSDrH+8= X-HE-Tag: 1792591196-339773 X-HE-Meta: U2FsdGVkX1861IrJGKHJrw2YUaPAEp+L5jIF8Xes2eztiCZCrcW5nI1T+UayyKSJrzCKUOBCm/vLjjyOse14Li4T9MqGNicBvXmeC90QOZ28xh8dsIQxjo1OGZ3jeUxNQY5daAZKUHu3BMk253d5lrHSulnjiaoDelEuYpF/LE5k7AR558mM9VvOvBMz3hiAB8O6PmlPe8q9ZHuANJ71KuJs5TZAjxtsIj3jnAyQl/qF+roOK5pxz+lcF9L4mCSsr0Xk5HWgBefxOARZgje9oLUbunxeUfZa/7SKQOllMto2V/8ferq+z01v5FF4NUSljGtFt9GGsYkzkD9MYVt0tLDJ0m09zVVeJrETHLAhp7c9mdZgGws+wp/bAJ41v0vY On Wed, 21 Oct 2026 15:34:30 +0200 Peter Zijlstra wrote: > That simply doesn't work. > > Even *IF* memory stores would propagate instantly (they don't) you can > still have the boolean swap while in the middle of this state. > > --- > > B = true; > > CPU0 CPU1 > > enqueue > if (B) > something++; > > B = false; > > dequeue > if (B) > something--; > > > --- > > Will still be left with something unbalanced, even if everything is > super duper magically atomic. Fair point. -- Steve