From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.13]) (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 A31A71CA9E; Mon, 15 Jul 2024 16:07:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721059655; cv=none; b=AywUZ4HILrGfbKPP99jfGTVg0Pixa69MLku+Xz4KyD9NqLCdHJ0txoYASVOOYkRTBawYAzDmpeMqegq9zd7GABOgZlJfv2MTbqGaSs5BFQGjFlHGCbvkix41gVn/Uvx5hCGytBD4OMcH9hfnZlmm1wC8fyQcR16TVrhH1vdQjD0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721059655; c=relaxed/simple; bh=Sws7f9Vo49jdmhQbNZDTC7ZNdMCwPwHbF7VqYoaZz+g=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=e+4Vr0mr1vSelOW2Du/Fwv72nSeSWkgA3/NFCoWPuco5vypNvB+MHpTf/o7C7Ea/Hc8OiG0sedlFNify/Sm/jG+RXmgAX+dbj03tW4CVxGLXDPYRm8gN7FuUyRtKfqyNF5HcsGla484trlT4Dm506bUiDbKI50BOJC1Hi89gH5M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=NB7PWPFS; arc=none smtp.client-ip=192.198.163.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="NB7PWPFS" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1721059653; x=1752595653; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Sws7f9Vo49jdmhQbNZDTC7ZNdMCwPwHbF7VqYoaZz+g=; b=NB7PWPFS7c5KhHqMWhumEBCMqI4LRyrorBZIjsWwNmP2YaJ/F7youvoe rxNhWnU+5ZOynMY70aDsk576NZEQb57YYvAbYPul7WjRjdggjHmzNJIVM 7fDmD3ykHBuoAc+IDUHWnwfOewJVFtJmeKtQt8AgCRO6QJQ2bjC8cxc5U GcoNwPlmClYthJkpqf/fN6CI+LFHqbeXxcGn+B7aP72fUdNfLv9MpdIMk +DCQmPc6DTvuAzrO9gdO9mPfXPt1yuwvwDespmOLEwdQ+/CxYpGBT73FT 8j3cjN06nM7T+yQEqTOHU6PiJsJ64T/3EYqsDlUz9MZEfc+29SkvO3u2e g==; X-CSE-ConnectionGUID: ql2bUfEkT2S5oUgHB55SPA== X-CSE-MsgGUID: i4q5tJboQOCOs5DvdUITzw== X-IronPort-AV: E=McAfee;i="6700,10204,11134"; a="21361107" X-IronPort-AV: E=Sophos;i="6.09,210,1716274800"; d="scan'208";a="21361107" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jul 2024 09:07:33 -0700 X-CSE-ConnectionGUID: dZT8mAPQT5y9zf0gTjYJBg== X-CSE-MsgGUID: 065qeGZMRZenPeuhJD/43A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.09,210,1716274800"; d="scan'208";a="49413493" Received: from ahunter6-mobl1.ger.corp.intel.com (HELO localhost.localdomain) ([10.246.49.253]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jul 2024 09:07:27 -0700 From: Adrian Hunter To: Peter Zijlstra Cc: Ingo Molnar , Mark Rutland , Alexander Shishkin , Heiko Carstens , Thomas Richter , Hendrik Brueckner , Suzuki K Poulose , Mike Leach , James Clark , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, Yicong Yang , Jonathan Cameron , Will Deacon , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Ian Rogers , Andi Kleen , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH V9 01/13] perf/x86/intel/pt: Fix sampling synchronization Date: Mon, 15 Jul 2024 19:07:00 +0300 Message-Id: <20240715160712.127117-2-adrian.hunter@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240715160712.127117-1-adrian.hunter@intel.com> References: <20240715160712.127117-1-adrian.hunter@intel.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Content-Transfer-Encoding: 8bit pt_event_snapshot_aux() uses pt->handle_nmi to determine if tracing needs to be stopped, however tracing can still be going because pt->handle_nmi is set to zero before tracing is stopped in pt_event_stop, whereas pt_event_snapshot_aux() requires that tracing must be stopped in order to copy a sample of trace from the buffer. Instead call pt_config_stop() always, which anyway checks config for RTIT_CTL_TRACEEN and does nothing if it is already clear. Note pt_event_snapshot_aux() can continue to use pt->handle_nmi to determine if the trace needs to be restarted afterwards. Fixes: 25e8920b301c ("perf/x86/intel/pt: Add sampling support") Cc: stable@vger.kernel.org Signed-off-by: Adrian Hunter --- Changes in V9: New patch arch/x86/events/intel/pt.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index 14db6d9d318b..6aaa21729589 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -1606,6 +1606,7 @@ static void pt_event_stop(struct perf_event *event, int mode) * see comment in intel_pt_interrupt(). */ WRITE_ONCE(pt->handle_nmi, 0); + barrier(); pt_config_stop(event); @@ -1657,11 +1658,10 @@ static long pt_event_snapshot_aux(struct perf_event *event, return 0; /* - * Here, handle_nmi tells us if the tracing is on + * There is no PT interrupt in this mode, so stop the trace and it will + * remain stopped while the buffer is copied. */ - if (READ_ONCE(pt->handle_nmi)) - pt_config_stop(event); - + pt_config_stop(event); pt_read_offset(buf); pt_update_head(pt); @@ -1673,11 +1673,10 @@ static long pt_event_snapshot_aux(struct perf_event *event, ret = perf_output_copy_aux(&pt->handle, handle, from, to); /* - * If the tracing was on when we turned up, restart it. - * Compiler barrier not needed as we couldn't have been - * preempted by anything that touches pt->handle_nmi. + * Here, handle_nmi tells us if the tracing was on. + * If the tracing was on, restart it. */ - if (pt->handle_nmi) + if (READ_ONCE(pt->handle_nmi)) pt_config_start(event); return ret; -- 2.34.1