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 BCADB1D0492; Tue, 15 Oct 2024 11:52:58 +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=1728993178; cv=none; b=RtWf8mWq894347hAi/NI5SCvUqUOI7eCsv6N3B27qJK6f0+VF0zqVaCrEyAH2rqk98GJkGzVt6aN5RCpVSq99STox85K5uxcsEUzn1JkbPvDmHOWNNRUh+lKD/GTGqMV02KiVN70jdliz+CIyqinc34MWIOJde81U1tyI9o3fBE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728993178; c=relaxed/simple; bh=ON18hNAHUfmsHnnhQ5CQe9S6DbsQHM+0rV5n0DzjZTk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YpLa6mUhPCC7goD8TzjvnjQpbAs/a5a7BoojK0lyX5SyqJF/MQ5+ZJw+177J+b2pYhu0H3SDMAG8Dmc2aMkNozyDIK0E6U3ADWidYwb0akbyMbKuYkdjsEKftqjfYqvKp1i33/hu2DrVYmxZDAGRFj+X8SsYi4D5jnprtVAAMHk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=HZJoTOt3; 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="HZJoTOt3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2BD94C4CEC6; Tue, 15 Oct 2024 11:52:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1728993178; bh=ON18hNAHUfmsHnnhQ5CQe9S6DbsQHM+0rV5n0DzjZTk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HZJoTOt3Z5b+scmLq6F0ce1MhqRkqSB0Iz8/Vpk8NFmm3Z2mCztIHHhgsTX8WTKf7 eVwBDEE6Pc1YltVvoTJjEvcn7M3sEMuL1VbitZetA/nXnBwAsK+Lcm0fZ3EJX0CBcR bntGMxa+Fis1paqkEunEdLK3rlbzta+j3p7+ZZaY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Adrian Hunter , "Peter Zijlstra (Intel)" Subject: [PATCH 5.15 334/691] perf/x86/intel/pt: Fix sampling synchronization Date: Tue, 15 Oct 2024 13:24:42 +0200 Message-ID: <20241015112453.590731450@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241015112440.309539031@linuxfoundation.org> References: <20241015112440.309539031@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-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 @@ -1586,6 +1586,7 @@ 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); @@ -1637,11 +1638,10 @@ 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); @@ -1653,11 +1653,10 @@ 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;