From patchwork Mon Nov 27 15:12:47 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Petr Pavlu X-Patchwork-Id: 170222 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:ce62:0:b0:403:3b70:6f57 with SMTP id o2csp3200563vqx; Mon, 27 Nov 2023 07:13:21 -0800 (PST) X-Google-Smtp-Source: AGHT+IHKpQRtNKvyYoxL/gu4bunSNNVifZTukN/0lmKOQUhpCi5xtGGLivIAto/1ztXQTM0Qzjmh X-Received: by 2002:a05:6a00:acc:b0:6cd:8436:e19 with SMTP id c12-20020a056a000acc00b006cd84360e19mr4203864pfl.19.1701098001011; Mon, 27 Nov 2023 07:13:21 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1701098000; cv=none; d=google.com; s=arc-20160816; b=gcrxX8Xdp+wfxwbV+sa2ZtAQfzE605+YQRFiTOBqXgczka/JbRkvG+WZCuCudtZcjv al3ETiciC78siI0C2u5Rfc2/MBDgGC+kyuwfo6okNJ09Bf232SSvoui8Xoda4T8hYnkH qO+mFxwSKf+877dYmJ5wRHBZwJzRFAFEHMMi276CrfjcmCN4yGqHkLNFSCO1T08ycIDb FyN1Vj6ArGOPWN/pMImynENtctmj8l/F+5Ig7zcdBTtysyZ1WiaJwkC29tqgzz/K3Gn4 GLyjIAOiZdEk9621c9YMqDXVdcVgDoeI3kwUBeubj5u0Vmlf4pK+mJFQ0FUzNVYnQsCW dmiQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=RZOede/GVo/356zeYBXrhUm1bQx9ZUkKq4X32mUMuI0=; fh=j8Hw7lilfJM9L0BwDk5YbNksoIL60jpocmP7dOg/RPw=; b=No40VRvZHLHWWveuHChzTpfD1i2SYLBh1OouMqKCm/5k1NgMZQ9XN10dvRqsKe944z s7aF6mE67mD2syxHFonjCNyRwOhrNBTyi9kyjiinYsRonoTw+fAuqFZENE99lE5oR5oG lv2wxJgWF3ekwNfPbNI0rZQo1qfvOYgpQxsD3Ul+dO3kUTuyHbXNz5scGEyv4pAN2QE6 Zjat/jhxxp7zfKYOB7VqgO1swsR48ppvwSQ+vJFbGBefwVMHLmhmp9oxRqZBX773h8a9 PfKpmMCV5Y6QBT/Dy36Zyg0DxhpoWCebP+YTnnDGBZYKbi1JurR4RrqxJGewVjBuyOg0 Jx7g== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=suse.com Received: from snail.vger.email (snail.vger.email. [23.128.96.37]) by mx.google.com with ESMTPS id l12-20020a65680c000000b00584e731e7fbsi9507448pgt.280.2023.11.27.07.13.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Nov 2023 07:13:20 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=suse.com Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by snail.vger.email (Postfix) with ESMTP id 73E3080A0546; Mon, 27 Nov 2023 07:13:18 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at snail.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233890AbjK0PNF (ORCPT + 99 others); Mon, 27 Nov 2023 10:13:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58236 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233845AbjK0PND (ORCPT ); Mon, 27 Nov 2023 10:13:03 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23718AA; Mon, 27 Nov 2023 07:13:09 -0800 (PST) Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 9D08521B1E; Mon, 27 Nov 2023 15:13:07 +0000 (UTC) Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 81A671367B; Mon, 27 Nov 2023 15:13:07 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap1.dmz-prg2.suse.org with ESMTPSA id iBsVHwOyZGXEPgAAD6G6ig (envelope-from ); Mon, 27 Nov 2023 15:13:07 +0000 From: Petr Pavlu To: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com Cc: zhengyejian1@huawei.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Petr Pavlu Subject: [PATCH 1/2] tracing: Simplify and fix "buffered event" synchronization Date: Mon, 27 Nov 2023 16:12:47 +0100 Message-Id: <20231127151248.7232-2-petr.pavlu@suse.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20231127151248.7232-1-petr.pavlu@suse.com> References: <20231127151248.7232-1-petr.pavlu@suse.com> MIME-Version: 1.0 X-Spamd-Bar: +++++++++++++++ Authentication-Results: smtp-out1.suse.de; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=suse.com (policy=quarantine); spf=fail (smtp-out1.suse.de: domain of petr.pavlu@suse.com does not designate 2a07:de40:b281:104:10:150:64:97 as permitted sender) smtp.mailfrom=petr.pavlu@suse.com X-Rspamd-Server: rspamd2 X-Spamd-Result: default: False [15.00 / 50.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_SPF_FAIL(1.00)[-all]; ARC_NA(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; R_MISSING_CHARSET(2.50)[]; MIME_GOOD(-0.10)[text/plain]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; BROKEN_CONTENT_TYPE(1.50)[]; DMARC_POLICY_QUARANTINE(1.50)[suse.com : No valid SPF, No valid DKIM,quarantine]; RCVD_COUNT_THREE(0.00)[3]; MX_GOOD(-0.01)[]; RCPT_COUNT_SEVEN(0.00)[7]; MID_CONTAINS_FROM(1.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(2.20)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] X-Spam-Score: 15.00 X-Rspamd-Queue-Id: 9D08521B1E X-Spam: Yes X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Mon, 27 Nov 2023 07:13:18 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1783730531906992376 X-GMAIL-MSGID: 1783730537917874147 The following warning appears when using buffered events: [ 203.556451] WARNING: CPU: 53 PID: 10220 at kernel/trace/ring_buffer.c:3912 ring_buffer_discard_commit+0x2eb/0x420 [...] [ 203.670690] CPU: 53 PID: 10220 Comm: stress-ng-sysin Tainted: G E 6.7.0-rc2-default #4 56e6d0fcf5581e6e51eaaecbdaec2a2338c80f3a [ 203.670704] Hardware name: Intel Corp. GROVEPORT/GROVEPORT, BIOS GVPRCRB1.86B.0016.D04.1705030402 05/03/2017 [ 203.670709] RIP: 0010:ring_buffer_discard_commit+0x2eb/0x420 [ 203.735721] Code: 4c 8b 4a 50 48 8b 42 48 49 39 c1 0f 84 b3 00 00 00 49 83 e8 01 75 b1 48 8b 42 10 f0 ff 40 08 0f 0b e9 fc fe ff ff f0 ff 47 08 <0f> 0b e9 77 fd ff ff 48 8b 42 10 f0 ff 40 08 0f 0b e9 f5 fe ff ff [ 203.735734] RSP: 0018:ffffb4ae4f7b7d80 EFLAGS: 00010202 [ 203.735745] RAX: 0000000000000000 RBX: ffffb4ae4f7b7de0 RCX: ffff8ac10662c000 [ 203.735754] RDX: ffff8ac0c750be00 RSI: ffff8ac10662c000 RDI: ffff8ac0c004d400 [ 203.781832] RBP: ffff8ac0c039cea0 R08: 0000000000000000 R09: 0000000000000000 [ 203.781839] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 203.781842] R13: ffff8ac10662c000 R14: ffff8ac0c004d400 R15: ffff8ac10662c008 [ 203.781846] FS: 00007f4cd8a67740(0000) GS:ffff8ad798880000(0000) knlGS:0000000000000000 [ 203.781851] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 203.781855] CR2: 0000559766a74028 CR3: 00000001804c4000 CR4: 00000000001506f0 [ 203.781862] Call Trace: [ 203.781870] [ 203.851949] trace_event_buffer_commit+0x1ea/0x250 [ 203.851967] trace_event_raw_event_sys_enter+0x83/0xe0 [ 203.851983] syscall_trace_enter.isra.0+0x182/0x1a0 [ 203.851990] do_syscall_64+0x3a/0xe0 [ 203.852075] entry_SYSCALL_64_after_hwframe+0x6e/0x76 [ 203.852090] RIP: 0033:0x7f4cd870fa77 [ 203.982920] Code: 00 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 90 b8 89 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 43 0e 00 f7 d8 64 89 01 48 [ 203.982932] RSP: 002b:00007fff99717dd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000089 [ 203.982942] RAX: ffffffffffffffda RBX: 0000558ea1d7b6f0 RCX: 00007f4cd870fa77 [ 203.982948] RDX: 0000000000000000 RSI: 00007fff99717de0 RDI: 0000558ea1d7b6f0 [ 203.982957] RBP: 00007fff99717de0 R08: 00007fff997180e0 R09: 00007fff997180e0 [ 203.982962] R10: 00007fff997180e0 R11: 0000000000000246 R12: 00007fff99717f40 [ 204.049239] R13: 00007fff99718590 R14: 0000558e9f2127a8 R15: 00007fff997180b0 [ 204.049256] For instance, it can be triggered by running these two commands in parallel: $ while true; do echo hist:key=id.syscall:val=hitcount > \ /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger; done $ stress-ng --sysinfo $(nproc) The warning indicates that the current ring_buffer_per_cpu is not in the committing state. It happens because the active ring_buffer_event doesn't actually come from the ring_buffer_per_cpu but is allocated from trace_buffered_event. The bug is in function trace_buffered_event_disable() where the following normally happens: * The code invokes disable_trace_buffered_event() via smp_call_function_many() and follows it by synchronize_rcu(). This increments the per-CPU variable trace_buffered_event_cnt on each target CPU and grants trace_buffered_event_disable() the exclusive access to the per-CPU variable trace_buffered_event. * Maintenance is performed on trace_buffered_event, all per-CPU event buffers get freed. * The code invokes enable_trace_buffered_event() via smp_call_function_many(). This decrements trace_buffered_event_cnt and releases the access to trace_buffered_event. A problem is that smp_call_function_many() runs a given function on all target CPUs except on the current one. The following can then occur: * Task X executing trace_buffered_event_disable() runs on CPU A. * The control reaches synchronize_rcu() and the task gets rescheduled on another CPU B. * The RCU synchronization finishes. At this point, trace_buffered_event_disable() has the exclusive access to all trace_buffered_event variables except trace_buffered_event[A] because trace_buffered_event_cnt[A] is never incremented and if the buffer is currently unused, remains set to 0. * A different task Y is scheduled on CPU A and hits a trace event. The code in trace_event_buffer_lock_reserve() sees that trace_buffered_event_cnt[A] is set to 0 and decides the use the buffer provided by trace_buffered_event[A]. * Task X continues its execution in trace_buffered_event_disable(). The code incorrectly frees the event buffer pointed by trace_buffered_event[A] and resets the variable to NULL. * Task Y writes event data to the now freed buffer and later detects the created inconsistency. The issue is observable since commit dea499781a11 ("tracing: Fix warning in trace_buffered_event_disable()") which moved the call of trace_buffered_event_disable() in __ftrace_event_enable_disable() earlier, prior to invoking call->class->reg(.. TRACE_REG_UNREGISTER ..). The underlying problem in trace_buffered_event_disable() is however present since the original implementation in commit 0fc1b09ff1ff ("tracing: Use temp buffer when filtering events"). The bug is simply fixable by replacing smp_call_function_many() by on_each_cpu_mask(), but the code has other issues as well: * Function trace_event_buffer_lock_reserve() reads trace_buffered_event and trace_buffered_event_cnt in reverse order than they are written in trace_buffered_event_disable() and without any memory barrier. It could happen that trace_event_buffer_lock_reserve() still finds a valid pointer in trace_buffered_event which is being freed by trace_buffered_event_disable() but later already sees the decremented value of trace_buffered_event_cnt back to 0 and incorrectly decides to use the provided buffer. * Function trace_buffered_event_enable() initializes memory of each allocated trace_buffered_event to zero but no memory barrier is present to ensure this operation is completed before publishing its pointer for use in trace_event_buffer_lock_reserve(). * Calling function trace_buffered_event_enable() normally requires pairing it with trace_buffered_event_disable(). However, the function has no error return code and in case of a failure decrements back trace_buffered_event_ref. This results in underflow of the counter when trace_buffered_event_disable() gets called later. These problems can be addressed individually but it looks better to rework the synchronization mechanism and simplify it in the first place. Instead of using the per-CPU variable trace_buffered_event_cnt for the exclusive access during the disable operation, introduce a new variable trace_buffered_event_enabled to reflect the current state and appropriately adjust the code. The variable indicates whether buffered events are currently enabled and trace_buffered_event together with trace_buffered_event_cnt are ok to use. The updated synchronization mechanism fixes the mentioned problems and avoids also sending IPIs across the system. Fixes: 0fc1b09ff1ff ("tracing: Use temp buffer when filtering events") Fixes: dea499781a11 ("tracing: Fix warning in trace_buffered_event_disable()") Signed-off-by: Petr Pavlu --- kernel/trace/trace.c | 66 ++++++++++++++++++-------------------------- 1 file changed, 27 insertions(+), 39 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 9aebf904ff97..123acb9105dd 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2741,6 +2741,7 @@ trace_buffer_lock_reserve(struct trace_buffer *buffer, DEFINE_PER_CPU(struct ring_buffer_event *, trace_buffered_event); DEFINE_PER_CPU(int, trace_buffered_event_cnt); static int trace_buffered_event_ref; +static bool trace_buffered_event_enabled; /** * trace_buffered_event_enable - enable buffering events @@ -2764,7 +2765,9 @@ void trace_buffered_event_enable(void) WARN_ON_ONCE(!mutex_is_locked(&event_mutex)); - if (trace_buffered_event_ref++) + trace_buffered_event_ref++; + + if (trace_buffered_event_enabled) return; for_each_tracing_cpu(cpu) { @@ -2777,30 +2780,21 @@ void trace_buffered_event_enable(void) memset(event, 0, sizeof(*event)); per_cpu(trace_buffered_event, cpu) = event; - - preempt_disable(); - if (cpu == smp_processor_id() && - __this_cpu_read(trace_buffered_event) != - per_cpu(trace_buffered_event, cpu)) - WARN_ON_ONCE(1); - preempt_enable(); } + /* + * Ensure all initialization changes are visible and publish + * availability of trace_buffered_event. + */ + smp_wmb(); + WRITE_ONCE(trace_buffered_event_enabled, true); return; - failed: - trace_buffered_event_disable(); -} -static void enable_trace_buffered_event(void *data) -{ - /* Probably not needed, but do it anyway */ - smp_rmb(); - this_cpu_dec(trace_buffered_event_cnt); -} - -static void disable_trace_buffered_event(void *data) -{ - this_cpu_inc(trace_buffered_event_cnt); + failed: + for_each_tracing_cpu(cpu) { + free_page((unsigned long)per_cpu(trace_buffered_event, cpu)); + per_cpu(trace_buffered_event, cpu) = NULL; + } } /** @@ -2820,33 +2814,19 @@ void trace_buffered_event_disable(void) if (WARN_ON_ONCE(!trace_buffered_event_ref)) return; - if (--trace_buffered_event_ref) + if (--trace_buffered_event_ref || !trace_buffered_event_enabled) return; - preempt_disable(); - /* For each CPU, set the buffer as used. */ - smp_call_function_many(tracing_buffer_mask, - disable_trace_buffered_event, NULL, 1); - preempt_enable(); + WRITE_ONCE(trace_buffered_event_enabled, false); /* Wait for all current users to finish */ synchronize_rcu(); for_each_tracing_cpu(cpu) { + WARN_ON_ONCE(per_cpu(trace_buffered_event_cnt, cpu) != 0); free_page((unsigned long)per_cpu(trace_buffered_event, cpu)); per_cpu(trace_buffered_event, cpu) = NULL; } - /* - * Make sure trace_buffered_event is NULL before clearing - * trace_buffered_event_cnt. - */ - smp_wmb(); - - preempt_disable(); - /* Do the work on each cpu */ - smp_call_function_many(tracing_buffer_mask, - enable_trace_buffered_event, NULL, 1); - preempt_enable(); } static struct trace_buffer *temp_buffer; @@ -2883,9 +2863,16 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb, * is still quicker than no copy on match, but having * to discard out of the ring buffer on a failed match. */ - if ((entry = __this_cpu_read(trace_buffered_event))) { + if (READ_ONCE(trace_buffered_event_enabled)) { int max_len = PAGE_SIZE - struct_size(entry, array, 1); + /* + * Ensure per-CPU variables trace_buffered_event(_cnt) + * are read after trace_buffered_event_enabled, pairs + * with smp_wmb() in trace_buffered_event_enable(). + */ + smp_rmb(); + val = this_cpu_inc_return(trace_buffered_event_cnt); /* @@ -2906,6 +2893,7 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb, * handle the failure in that case. */ if (val == 1 && likely(len <= max_len)) { + entry = __this_cpu_read(trace_buffered_event); trace_event_setup(entry, type, trace_ctx); entry->array[0] = len; /* Return with preemption disabled */ From patchwork Mon Nov 27 15:12:48 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Petr Pavlu X-Patchwork-Id: 170223 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:ce62:0:b0:403:3b70:6f57 with SMTP id o2csp3200572vqx; Mon, 27 Nov 2023 07:13:21 -0800 (PST) X-Google-Smtp-Source: AGHT+IEfVo/TpoixpDANwvvnixAmVZIW+td0bJIwTHaHJlBiXvalaIMN82Th+eHXMn+qz9/tfZUQ X-Received: by 2002:a05:6870:6122:b0:1f9:34a6:4e3a with SMTP id s34-20020a056870612200b001f934a64e3amr13455292oae.43.1701098001596; Mon, 27 Nov 2023 07:13:21 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1701098001; cv=none; d=google.com; s=arc-20160816; b=yKX5Xhfbo/cVRUeVbGkoRFMFEkM8uJBbFogjJ/idVlRCztmF/LN5EYwr3GkmIDiTzE shVYFPVa63wgnfGXIbkngWN628gikjXhcFiSIT/FA8cIiZYb2fBMUlcx2z3fY481lMXJ 5otDsdZCF8KDY6wjVwZq37R1+K3T1f1LJ97/rO+fD++xXjvEn5UyaHZ1djup89oUEOsl kbfMENKlVwa2CSdKTqbb8GwoG71sh7QblBCRRRmeaVMVHIx9RFSSwChqiGDsMjNSAkRP oFEG7Ss/E0s7yaCWUm+kIAaxToghhwDr+bshdineX5UXrnjuZimZ9vAJTq+vjRzZxFy1 iD7Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from; bh=CXyOdoLaM0cNkr48/3X3wBWfZcujNhtVPgm/7hewXHQ=; fh=j8Hw7lilfJM9L0BwDk5YbNksoIL60jpocmP7dOg/RPw=; b=GgN7rDgJX85XHiuo8NNdHwbrQ/6Vc/0P3QlVnTxQdgsK73knwK1Uc/GwH2mod/FR3J DKr4pS+g5zQSmTI6ODEcX5Bl0GnVDqe+eJvh1opBzl5t+6iz4GLJQLtnpyocPSBFzwR6 M8iXIcOL/YxzawXs4tQPJXG4ChjLOiQFZxzSIBU4jOEroQcvYKufwB8pPyYAfjtKaQda ch+svJAqmIUWXIgj7ADAMOFWBn8GIUJZRxbuuEDoIOkqJWqhiSv1WtA2N+GzL36iB22f x80GGnYd6EvASoK48QLXfOpeWdIcYLL9bH+CCRgbMQsnwlfolk/qBuC1q+oIiVDrleOa uChw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=suse.com Received: from snail.vger.email (snail.vger.email. [2620:137:e000::3:7]) by mx.google.com with ESMTPS id cv20-20020a056870c69400b001d66918a314si3857813oab.2.2023.11.27.07.13.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Nov 2023 07:13:21 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=suse.com Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by snail.vger.email (Postfix) with ESMTP id 8DB9B80A054F; Mon, 27 Nov 2023 07:13:20 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at snail.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233899AbjK0PNI (ORCPT + 99 others); Mon, 27 Nov 2023 10:13:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233887AbjK0PNE (ORCPT ); Mon, 27 Nov 2023 10:13:04 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2a07:de40:b251:101:10:150:64:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 753B8BB; Mon, 27 Nov 2023 07:13:10 -0800 (PST) Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 15E121FBDB; Mon, 27 Nov 2023 15:13:09 +0000 (UTC) Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id E312C1367B; Mon, 27 Nov 2023 15:13:08 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap1.dmz-prg2.suse.org with ESMTPSA id +IZ3NgSyZGXEPgAAD6G6ig (envelope-from ); Mon, 27 Nov 2023 15:13:08 +0000 From: Petr Pavlu To: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com Cc: zhengyejian1@huawei.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Petr Pavlu Subject: [PATCH 2/2] tracing: Disable events in reverse order of their enable operation Date: Mon, 27 Nov 2023 16:12:48 +0100 Message-Id: <20231127151248.7232-3-petr.pavlu@suse.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20231127151248.7232-1-petr.pavlu@suse.com> References: <20231127151248.7232-1-petr.pavlu@suse.com> MIME-Version: 1.0 X-Spamd-Bar: +++++++++++++++ X-Spam-Score: 15.00 X-Rspamd-Server: rspamd1 Authentication-Results: smtp-out2.suse.de; dkim=none; spf=fail (smtp-out2.suse.de: domain of petr.pavlu@suse.com does not designate 2a07:de40:b281:104:10:150:64:97 as permitted sender) smtp.mailfrom=petr.pavlu@suse.com; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=suse.com (policy=quarantine) X-Rspamd-Queue-Id: 15E121FBDB X-Spamd-Result: default: False [15.00 / 50.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; R_MISSING_CHARSET(2.50)[]; BROKEN_CONTENT_TYPE(1.50)[]; RCVD_COUNT_THREE(0.00)[3]; MX_GOOD(-0.01)[]; NEURAL_HAM_SHORT(-0.19)[-0.948]; RCPT_COUNT_SEVEN(0.00)[7]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(2.20)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; R_SPF_FAIL(1.00)[-all]; FROM_HAS_DN(0.00)[]; DMARC_POLICY_QUARANTINE(1.50)[suse.com : No valid SPF, No valid DKIM,quarantine]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MID_CONTAINS_FROM(1.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCVD_TLS_ALL(0.00)[] X-Spam: Yes X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Mon, 27 Nov 2023 07:13:20 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1783730538004921520 X-GMAIL-MSGID: 1783730538004921520 Make the disable operation in __ftrace_event_enable_disable() use the reverse order of the respective enable operation. This has two minor benefits: * Disabling of buffered events via trace_buffered_event_disable() is done after unregistering the trace event. It closes a small window where an event would be still registered and could be hit, but would unnecessarily go directly to a ring buffer. * The SOFT_DISABLED flag is now consistently set only when SOFT_MODE is also set. Signed-off-by: Petr Pavlu --- kernel/trace/trace_events.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index f29e815ca5b2..5f14d68a0ced 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -633,9 +633,6 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file, if (atomic_dec_return(&file->sm_ref) > 0) break; disable = file->flags & EVENT_FILE_FL_SOFT_DISABLED; - clear_bit(EVENT_FILE_FL_SOFT_MODE_BIT, &file->flags); - /* Disable use of trace_buffered_event */ - trace_buffered_event_disable(); } else disable = !(file->flags & EVENT_FILE_FL_SOFT_MODE); @@ -653,11 +650,17 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file, call->class->reg(call, TRACE_REG_UNREGISTER, file); } - /* If in SOFT_MODE, just set the SOFT_DISABLE_BIT, else clear it */ - if (file->flags & EVENT_FILE_FL_SOFT_MODE) - set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags); - else + + if (soft_disable) { + /* Complete going out of SOFT_MODE */ clear_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags); + clear_bit(EVENT_FILE_FL_SOFT_MODE_BIT, &file->flags); + /* Disable use of trace_buffered_event */ + trace_buffered_event_disable(); + } else if (file->flags & EVENT_FILE_FL_SOFT_MODE) { + /* If in SOFT_MODE, just set the SOFT_DISABLE_BIT */ + set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags); + } break; case 1: /*