From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7F8BA1D0438; Wed, 2 Oct 2024 14:46:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727880416; cv=none; b=ZDg10zJCss9/brPGdoNdkO8Ihpbmz1GJYqm4UCFu2/4q2wdvwXWTh/BReD1ILB1/NZKceehjIpbVm97i259hXef0ar+27C3SSVBMOgl9JepRfPRJ/6vu7bGToTLp7dlbbqyBFc5tcJU8HY6VTtOiDCeWV88Us7ozoFCJhtal7YI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727880416; c=relaxed/simple; bh=MCtMhi/DWxFrGB5vWb2C8bIiG4sxKzeip+R2wrnXD6E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DyQ9JEGmpmO6rfMEnE48HWGoKEn1mc/enOrC3Sc+QrREKlg2Z378cEq1+CxO6OgJjBT3Z8o7sW6YGeN6c6GVTR5wtGRZ8QXdmvmOLd9dsukag7Q6x7i9DXBboV6kniMK+j1hCJYTlEEtOPSnio9IfOdQ2i+m4QzfZg3XnQQGPzM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nZT2ncq5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="nZT2ncq5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0BB96C4CEC2; Wed, 2 Oct 2024 14:46:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1727880416; bh=MCtMhi/DWxFrGB5vWb2C8bIiG4sxKzeip+R2wrnXD6E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nZT2ncq5lOT9oIC2gHLFQgfssCmbc9njIg/W2sM9YVm8XYif09FzCGq1S4lPevcPX jDH3o1KorLFTigxaHNv3MP7wYBJQONV+yPktyJTo7jD0QLynXnHMp9nxbwdXMrxgcl 2Sv1fgY9tpDl+aHDwwExJ9/YRTL6aidmLpNyejvI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Adrian Hunter , "Peter Zijlstra (Intel)" Subject: [PATCH 6.6 451/538] perf/x86/intel/pt: Fix sampling synchronization Date: Wed, 2 Oct 2024 15:01:30 +0200 Message-ID: <20241002125810.243575764@linuxfoundation.org> X-Mailer: git-send-email 2.46.2 In-Reply-To: <20241002125751.964700919@linuxfoundation.org> References: <20241002125751.964700919@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Adrian Hunter commit d92792a4b26e50b96ab734cbe203d8a4c932a7a9 upstream. 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") Signed-off-by: Adrian Hunter Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20240715160712.127117-2-adrian.hunter@intel.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/events/intel/pt.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -1602,6 +1602,7 @@ static void pt_event_stop(struct perf_ev * see comment in intel_pt_interrupt(). */ WRITE_ONCE(pt->handle_nmi, 0); + barrier(); pt_config_stop(event); @@ -1653,11 +1654,10 @@ static long pt_event_snapshot_aux(struct 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); @@ -1669,11 +1669,10 @@ static long pt_event_snapshot_aux(struct 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;