From patchwork Tue Oct 27 13:49:13 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 313005 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC1F8C56202 for ; Tue, 27 Oct 2020 14:12:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A61322076A for ; Tue, 27 Oct 2020 14:12:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807961; bh=GSSLgrf3AqyB6OCdMg++2K2BifGe1iyz5aF0Zxywr4w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=P9qXqkpG4U0bawnnzG96i0mcw8yGibW+nitNo3Io6pqZzS+oWLVYOf8K3lor33jou Vb14cwYSACm0OCH8oAX6cmblmyP7VsY8YzkSwtSqM604Zzyj54yPRQRb/5O1LR+O+o WLY9M3Dg0Ro5PmDooOcIzT3dnX1HPDZlFdCFeurs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733457AbgJ0OMk (ORCPT ); Tue, 27 Oct 2020 10:12:40 -0400 Received: from mail.kernel.org ([198.145.29.99]:33616 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756302AbgJ0OM0 (ORCPT ); Tue, 27 Oct 2020 10:12:26 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DF4F22076A; Tue, 27 Oct 2020 14:12:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807945; bh=GSSLgrf3AqyB6OCdMg++2K2BifGe1iyz5aF0Zxywr4w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mH8LFMW+Lydh5OFM5S6QfMzuAfA4Moa00Zmswm0neTznJB2fK82Bw6TONpxcexPCj PzDshTbLXPsjsdaD+h/1Shcyv12CJ9+fsRaPlk0q0nP2icCblc2jWx8P36nQiG26dy OfluaNHXE6lNpwEs8pIJDxV/8uO59VDqjU97w96Y= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Adrian Hunter , Andi Kleen , Jiri Olsa , Yu-cheng Yu , Arnaldo Carvalho de Melo , Sasha Levin Subject: [PATCH 4.14 098/191] perf intel-pt: Fix "context_switch event has no tid" error Date: Tue, 27 Oct 2020 14:49:13 +0100 Message-Id: <20201027134914.415084049@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027134909.701581493@linuxfoundation.org> References: <20201027134909.701581493@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Adrian Hunter [ Upstream commit 7d537a8d2e76bc4fc71e34545ceaa463ac2cd928 ] A context_switch event can have no tid because pids can be detached from a task while the task is still running (in do_exit()). Note this won't happen with per-task contexts because then tracing stops at perf_event_exit_task() If a task with no tid gets preempted, or a dying task gets preempted and its parent releases it, when it subsequently gets switched back in, Intel PT will not be able to determine what task is running and prints an error "context_switch event has no tid". However, it is not really an error because the task is in kernel space and the decoder can continue to decode successfully. Fix by changing the error to be only a logged message, and make allowance for tid == -1. Example: Using 5.9-rc4 with Preemptible Kernel (Low-Latency Desktop) e.g. $ uname -r 5.9.0-rc4 $ grep PREEMPT .config # CONFIG_PREEMPT_NONE is not set # CONFIG_PREEMPT_VOLUNTARY is not set CONFIG_PREEMPT=y CONFIG_PREEMPT_COUNT=y CONFIG_PREEMPTION=y CONFIG_PREEMPT_RCU=y CONFIG_PREEMPT_NOTIFIERS=y CONFIG_DRM_I915_PREEMPT_TIMEOUT=640 CONFIG_DEBUG_PREEMPT=y # CONFIG_PREEMPT_TRACER is not set # CONFIG_PREEMPTIRQ_DELAY_TEST is not set Before: $ cat forkit.c #include #include #include int main() { pid_t child; int status = 0; child = fork(); if (child == 0) return 123; wait(&status); return 0; } $ gcc -o forkit forkit.c $ sudo ~/bin/perf record --kcore -a -m,64M -e intel_pt/cyc/k & [1] 11016 $ taskset 2 ./forkit $ sudo pkill perf $ [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 17.262 MB perf.data ] [1]+ Terminated sudo ~/bin/perf record --kcore -a -m,64M -e intel_pt/cyc/k $ sudo ~/bin/perf script --show-task-events --show-switch-events --itrace=iqqe-o -C 1 --ns | grep -C 2 forkit context_switch event has no tid taskset 11019 [001] 66663.270045029: 1 instructions:k: ffffffffb1d9f844 strnlen_user+0xb4 ([kernel.kallsyms]) taskset 11019 [001] 66663.270201816: 1 instructions:k: ffffffffb1a83121 unmap_page_range+0x561 ([kernel.kallsyms]) forkit 11019 [001] 66663.270327553: PERF_RECORD_COMM exec: forkit:11019/11019 forkit 11019 [001] 66663.270420028: 1 instructions:k: ffffffffb1db9537 __clear_user+0x27 ([kernel.kallsyms]) forkit 11019 [001] 66663.270648704: 1 instructions:k: ffffffffb18829e6 do_user_addr_fault+0xf6 ([kernel.kallsyms]) forkit 11019 [001] 66663.270833163: 1 instructions:k: ffffffffb230a825 irqentry_exit_to_user_mode+0x15 ([kernel.kallsyms]) forkit 11019 [001] 66663.271092359: 1 instructions:k: ffffffffb1aea3d9 lock_page_memcg+0x9 ([kernel.kallsyms]) forkit 11019 [001] 66663.271207092: PERF_RECORD_FORK(11020:11020):(11019:11019) forkit 11019 [001] 66663.271234775: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 11020/11020 forkit 11020 [001] 66663.271238407: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11019/11019 forkit 11020 [001] 66663.271312066: 1 instructions:k: ffffffffb1a88140 handle_mm_fault+0x10 ([kernel.kallsyms]) forkit 11020 [001] 66663.271476225: PERF_RECORD_EXIT(11020:11020):(11019:11019) forkit 11020 [001] 66663.271497488: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 11019/11019 forkit 11019 [001] 66663.271500523: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11020/11020 forkit 11019 [001] 66663.271517241: 1 instructions:k: ffffffffb24012cd error_entry+0x6d ([kernel.kallsyms]) forkit 11019 [001] 66663.271664080: PERF_RECORD_EXIT(11019:11019):(1386:1386) After: $ sudo ~/bin/perf script --show-task-events --show-switch-events --itrace=iqqe-o -C 1 --ns | grep -C 2 forkit taskset 11019 [001] 66663.270045029: 1 instructions:k: ffffffffb1d9f844 strnlen_user+0xb4 ([kernel.kallsyms]) taskset 11019 [001] 66663.270201816: 1 instructions:k: ffffffffb1a83121 unmap_page_range+0x561 ([kernel.kallsyms]) forkit 11019 [001] 66663.270327553: PERF_RECORD_COMM exec: forkit:11019/11019 forkit 11019 [001] 66663.270420028: 1 instructions:k: ffffffffb1db9537 __clear_user+0x27 ([kernel.kallsyms]) forkit 11019 [001] 66663.270648704: 1 instructions:k: ffffffffb18829e6 do_user_addr_fault+0xf6 ([kernel.kallsyms]) forkit 11019 [001] 66663.270833163: 1 instructions:k: ffffffffb230a825 irqentry_exit_to_user_mode+0x15 ([kernel.kallsyms]) forkit 11019 [001] 66663.271092359: 1 instructions:k: ffffffffb1aea3d9 lock_page_memcg+0x9 ([kernel.kallsyms]) forkit 11019 [001] 66663.271207092: PERF_RECORD_FORK(11020:11020):(11019:11019) forkit 11019 [001] 66663.271234775: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 11020/11020 forkit 11020 [001] 66663.271238407: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11019/11019 forkit 11020 [001] 66663.271312066: 1 instructions:k: ffffffffb1a88140 handle_mm_fault+0x10 ([kernel.kallsyms]) forkit 11020 [001] 66663.271476225: PERF_RECORD_EXIT(11020:11020):(11019:11019) forkit 11020 [001] 66663.271497488: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 11019/11019 forkit 11019 [001] 66663.271500523: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11020/11020 forkit 11019 [001] 66663.271517241: 1 instructions:k: ffffffffb24012cd error_entry+0x6d ([kernel.kallsyms]) forkit 11019 [001] 66663.271664080: PERF_RECORD_EXIT(11019:11019):(1386:1386) forkit 11019 [001] 66663.271688752: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: -1/-1 :-1 -1 [001] 66663.271692086: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11019/11019 :-1 -1 [001] 66663.271707466: 1 instructions:k: ffffffffb18eb096 update_load_avg+0x306 ([kernel.kallsyms]) Fixes: 86c2786994bd7c ("perf intel-pt: Add support for PERF_RECORD_SWITCH") Signed-off-by: Adrian Hunter Cc: Andi Kleen Cc: Jiri Olsa Cc: Yu-cheng Yu Link: http://lore.kernel.org/lkml/20200909084923.9096-3-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin --- tools/perf/util/intel-pt.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c index e8e05e7838b26..66591e8e26470 100644 --- a/tools/perf/util/intel-pt.c +++ b/tools/perf/util/intel-pt.c @@ -906,6 +906,8 @@ static void intel_pt_set_pid_tid_cpu(struct intel_pt *pt, if (queue->tid == -1 || pt->have_sched_switch) { ptq->tid = machine__get_current_tid(pt->machine, ptq->cpu); + if (ptq->tid == -1) + ptq->pid = -1; thread__zput(ptq->thread); } @@ -1948,10 +1950,8 @@ static int intel_pt_context_switch(struct intel_pt *pt, union perf_event *event, tid = sample->tid; } - if (tid == -1) { - pr_err("context_switch event has no tid\n"); - return -EINVAL; - } + if (tid == -1) + intel_pt_log("context_switch event has no tid\n"); intel_pt_log("context_switch: cpu %d pid %d tid %d time %"PRIu64" tsc %#"PRIx64"\n", cpu, pid, tid, sample->time, perf_time_to_tsc(sample->time,