From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out203-205-221-164.mail.qq.com (out203-205-221-164.mail.qq.com [203.205.221.164]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0ACD16FB5; Sat, 2 Mar 2024 04:42:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=203.205.221.164 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709354552; cv=none; b=ugI0VIh7op+rMSNC+oL3fZ/Uc4l22nq92gC0lknMi9UKx42K/491eyCf2Te+fZs+wHp7X9skUxNVaKL7Abm4LpTgF4vXPe1vZQb5+CI5Sv0uJG88CF0Jn7hl9E6MBxG8FU9lOLgnsWmTozEQ/RnFFezHPm4beh3gAZ11ohSInBc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709354552; c=relaxed/simple; bh=AYNv0Qa+glncn08+EPqSMHZm6uafarEkSus+rf9dSuo=; h=Message-ID:From:To:Cc:Subject:Date:In-Reply-To:References: MIME-Version; b=f0FbkAd151vgFZtR4hBGOtSOTyehD0ahDJLBIbDHkOffcbCqsIgwA6wTygQ2wu7c9kVe2qRH2vpOOnD5Sfj8LekSW9FGjiivzKEGU/0DVUszhm1n8HPluH++9VYmzSspcIhZqgZuPQvxIKn7jHHBALSHIe6jxU6O+JjGXE0Oy0o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=qq.com; spf=pass smtp.mailfrom=qq.com; dkim=pass (1024-bit key) header.d=qq.com header.i=@qq.com header.b=YF0UOb8Q; arc=none smtp.client-ip=203.205.221.164 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=qq.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=qq.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=qq.com header.i=@qq.com header.b="YF0UOb8Q" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qq.com; s=s201512; t=1709354545; bh=QAYg13vLJCBT7+EvsgOXj1+cDzAIKbXlvs3Jgvb8Qe8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=YF0UOb8QiOa4mahLo7PdXZXh1anjru25EfSN2td0e5jADQJ6t+D59+i3oespw+WAr xb5wGWAPuSFVbzxsf32QBSX7YpDXHp3fSOdctyhBrk4a+V1/utoQvMft7dNev4qFkh kkwXS1YE+vEgRerlUW73nskjYQyKUv9NqS0aASxA= Received: from localhost.localdomain ([218.94.142.74]) by newxmesmtplogicsvrsza1-0.qq.com (NewEsmtp) with SMTP id A979A8DF; Sat, 02 Mar 2024 12:42:23 +0800 X-QQ-mid: xmsmtpt1709354543t46hz37ko Message-ID: X-QQ-XMAILINFO: NXBlMEyQi3goJyrVn5XSQtitzC/kO4MLGqqSAWWC3LZ+U+w5hik6q17yobNOlr s1fH0FSQrI0Y26toV6TSEIisPbPeMSTtDMt/ybCuVc7ocX7laYTLReTRMRU410PWXKfo2VvxkEm4 QUT8AaeoOcsNUpwvRFB0zulllc6W6f+gF2F7uh7/bgFfl5MpeJPGWDMEnxFNouZj7zgOMJ8ascF0 KYXGwa+o+C30badC5YuM74S7xzS0jzAeNf3vaLQhkcWYHUAe+O5UX/BAKwbJLaQC6Z/AUEyCjLW7 A5YiNe0q5sThH82vMGsqJ4hll4W2Ev8hpuXyMwwYjkpjqXPiVofplLPT/2n66Jb+eDdLeXeAfIhu 9WwabG4z7SLZXh1fuYXUz0bpPWDcrK8MK21W634Z6qt0rwmznl8MRbHm3X7RcaPFN2PFK8KwNOhU M/djdlF0cjuJ3kb8hpmAakV+0gYhzZfZxH1itbFs+m12ynjb+0hQMtqyBx/9DjlaNXB2GYer8hrS He8KwbncIYyHklFPsjM+ZSqPLzGbYfLNie6pSIyDvyAYLtwSX8/1CGOa6fC/i55R0XtQSOyEIVam r2Mi41Pid4LlvW0ERygOBwgBHJaeE2P/sR3po4WpaclcWHmd5ev8GkO7z8rnbPJIF9m3bqxLIauS Rp5Y7C6lltieZoQtiBzZFMH/tyju+IsOXH+b71xY2AvphYZl30ILK2s/XvZ/SB/K2EdzYgowSnE7 l+QvvDMAG/Y6JxLkI9JvZmn7XZ2emLeW8FgXzDEWr9PlKr4BxEhkaKUZox3M8lgDSV18giuSG8CR g4+Kg/DSq/1MtL0QYisYtj479KIeJwUx1x4KKAhSSAQ9/tmCvBwxgGeBNe9D5deYkQkQVTDnPboX i++HOT2VSrSqX3g8HiB2uE+9XLHO8TJXmGe/D8f72zc3tTMN5EKvlgggnW8MQuzwviTpOHJ7fkpK Sc9R5ETOk+kFtFld96Ver6rHL1ajNbA/Oq7ZaQ5qt2i0xLInWuYM7sZI5pWUo6zLgtArzhA09oan X9VTsAUTHcCOosOJEAFlurw7/+89rApd9M+Tnh3n61+I/fkSWD X-QQ-XMRINFO: OWPUhxQsoeAVDbp3OJHYyFg= From: linke li To: Cc: lilinke99@qq.com, Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH v2] ring-buffer: use READ_ONCE() to read cpu_buffer->commit_page in concurrent environment Date: Sat, 2 Mar 2024 12:42:21 +0800 X-OQ-MSGID: <20240302044221.49277-1-lilinke99@qq.com> X-Mailer: git-send-email 2.39.3 (Apple Git-145) In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In function ring_buffer_iter_empty(), cpu_buffer->commit_page is read while other threads may change it. It may cause the time_stamp that read in the next line come from a different page. Use READ_ONCE() to avoid having to reason about compiler optimizations now and in future. Signed-off-by: linke li --- v1 -> v2: only add READ_ONCE() to read cpu_buffer->commit_page, make change log clear kernel/trace/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 0699027b4f4c..c7203a436d3c 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -4337,7 +4337,7 @@ int ring_buffer_iter_empty(struct ring_buffer_iter *iter) cpu_buffer = iter->cpu_buffer; reader = cpu_buffer->reader_page; head_page = cpu_buffer->head_page; - commit_page = cpu_buffer->commit_page; + commit_page = READ_ONCE(cpu_buffer->commit_page); commit_ts = commit_page->page->time_stamp; /* -- 2.39.3 (Apple Git-145)