From patchwork Thu Jul 11 11:02:39 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Zijlstra X-Patchwork-Id: 13730362 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 BF90515A874; Thu, 11 Jul 2024 11:07:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720696050; cv=none; b=lA3a6RL2A2p/hppTrGcnWG5srawKTGIB6zbjwFh6BXOcil3Cl1nS78DniKOgzSCN9z1n/Xv89ASpsxHdAEzCQHSjt4cs3drmVKRmJvmd41nwuiJ3fqz0aaGrwd5R4knb3fTp1D7KMAClDsjibW4f0ajsweqO9hixmTWnpDiV/Vo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720696050; c=relaxed/simple; bh=namzImpKkAE0SeDauxvgo7e0qpH+mTqxwz/WBAvffQw=; h=Message-Id:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=ZEItV1K+XTJHl5zqLY8VVA1sbuiViadYboaXI3fEm9TBpTa36H7ux+jQk7Zb64uYrxIK93RqfJ/CKTfNl5l8zi2NJH889IuUDdoGRSkWOHMwJK8qRSoF+pVeq6qr/wCtEOyhzF0iyiTLO6fN1TC++GQkGkg9OoMSrOKIPqzIkCo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=j9RYO7cl; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="j9RYO7cl" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-Id:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=6enVwtxrhKY9z473ycfT5rwTE1B57qqsh+H+nST3cXo=; b=j9RYO7clZB4u3MSfWuo6QarfqL g3fesYOQpUjOrvUFPJSaLKFf3CoX9IcSzasNr3plfgpWx33Tu87SOV3mtZR8drNmygV0azoTNQk3U o/krgOwILVlvsXGUAUrWnpX0omF1MKpcbTCCy92kiJyf3AZYG0JEMO7KF/yDSmih9y/bfMEyt2XOh 4rmL/+GlqJtbPYMBGpyJqCU510Avjaz8RXDt2xW41+2PnPpzEMbSD1eB40M9J3v/UNM4Q/gkaQ/Be gJ811YzpFRsvZMOW8MfIZ1i90lMDBJcEv4bbdVEt10VuoqOBnAmZND8ksrP7Vjb+1phnH1PQIwRr9 /fxd45Dw==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sRrdz-0000000Ax6R-22mg; Thu, 11 Jul 2024 11:07:23 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id C1463302182; Thu, 11 Jul 2024 13:07:22 +0200 (CEST) Message-Id: <20240711110400.635302571@infradead.org> User-Agent: quilt/0.65 Date: Thu, 11 Jul 2024 13:02:39 +0200 From: Peter Zijlstra To: mingo@kernel.org, andrii@kernel.org, oleg@redhat.com Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, peterz@infradead.org, rostedt@goodmis.org, mhiramat@kernel.org, jolsa@kernel.org, clm@meta.com, paulmck@kernel.org Subject: [PATCH v2 04/11] perf/uprobe: RCU-ify find_uprobe() References: <20240711110235.098009979@infradead.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 With handle_swbp() triggering concurrently on (all) CPUs, tree_lock becomes a bottleneck. Avoid treelock by doing RCU lookups of the uprobe. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Masami Hiramatsu (Google) --- kernel/events/uprobes.c | 49 +++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 40 insertions(+), 9 deletions(-) --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -40,6 +40,7 @@ static struct rb_root uprobes_tree = RB_ #define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree) static DEFINE_RWLOCK(uprobes_treelock); /* serialize rbtree access */ +static seqcount_rwlock_t uprobes_seqcount = SEQCNT_RWLOCK_ZERO(uprobes_seqcount, &uprobes_treelock); #define UPROBES_HASH_SZ 13 /* serialize uprobe->pending_list */ @@ -54,6 +55,7 @@ DEFINE_STATIC_PERCPU_RWSEM(dup_mmap_sem) struct uprobe { struct rb_node rb_node; /* node in the rb tree */ refcount_t ref; + struct rcu_head rcu; struct rw_semaphore register_rwsem; struct rw_semaphore consumer_rwsem; struct list_head pending_list; @@ -587,12 +589,25 @@ set_orig_insn(struct arch_uprobe *auprob *(uprobe_opcode_t *)&auprobe->insn); } +static struct uprobe *try_get_uprobe(struct uprobe *uprobe) +{ + if (refcount_inc_not_zero(&uprobe->ref)) + return uprobe; + return NULL; +} + static struct uprobe *get_uprobe(struct uprobe *uprobe) { refcount_inc(&uprobe->ref); return uprobe; } +static void uprobe_free_rcu(struct rcu_head *rcu) +{ + struct uprobe *uprobe = container_of(rcu, struct uprobe, rcu); + kfree(uprobe); +} + static void put_uprobe(struct uprobe *uprobe) { if (refcount_dec_and_test(&uprobe->ref)) { @@ -604,7 +619,7 @@ static void put_uprobe(struct uprobe *up mutex_lock(&delayed_uprobe_lock); delayed_uprobe_remove(uprobe, NULL); mutex_unlock(&delayed_uprobe_lock); - kfree(uprobe); + call_rcu(&uprobe->rcu, uprobe_free_rcu); } } @@ -653,10 +668,10 @@ static struct uprobe *__find_uprobe(stru .inode = inode, .offset = offset, }; - struct rb_node *node = rb_find(&key, &uprobes_tree, __uprobe_cmp_key); + struct rb_node *node = rb_find_rcu(&key, &uprobes_tree, __uprobe_cmp_key); if (node) - return get_uprobe(__node_2_uprobe(node)); + return try_get_uprobe(__node_2_uprobe(node)); return NULL; } @@ -667,20 +682,32 @@ static struct uprobe *__find_uprobe(stru */ static struct uprobe *find_uprobe(struct inode *inode, loff_t offset) { - struct uprobe *uprobe; + unsigned int seq; - read_lock(&uprobes_treelock); - uprobe = __find_uprobe(inode, offset); - read_unlock(&uprobes_treelock); + guard(rcu)(); - return uprobe; + do { + seq = read_seqcount_begin(&uprobes_seqcount); + struct uprobe *uprobe = __find_uprobe(inode, offset); + if (uprobe) { + /* + * Lockless RB-tree lookups are prone to false-negatives. + * If they find something, it's good. If they do not find, + * it needs to be validated. + */ + return uprobe; + } + } while (read_seqcount_retry(&uprobes_seqcount, seq)); + + /* Really didn't find anything. */ + return NULL; } static struct uprobe *__insert_uprobe(struct uprobe *uprobe) { struct rb_node *node; - node = rb_find_add(&uprobe->rb_node, &uprobes_tree, __uprobe_cmp); + node = rb_find_add_rcu(&uprobe->rb_node, &uprobes_tree, __uprobe_cmp); if (node) return get_uprobe(__node_2_uprobe(node)); @@ -702,7 +729,9 @@ static struct uprobe *insert_uprobe(stru struct uprobe *u; write_lock(&uprobes_treelock); + write_seqcount_begin(&uprobes_seqcount); u = __insert_uprobe(uprobe); + write_seqcount_end(&uprobes_seqcount); write_unlock(&uprobes_treelock); return u; @@ -936,7 +965,9 @@ static void delete_uprobe(struct uprobe return; write_lock(&uprobes_treelock); + write_seqcount_begin(&uprobes_seqcount); rb_erase(&uprobe->rb_node, &uprobes_tree); + write_seqcount_end(&uprobes_seqcount); write_unlock(&uprobes_treelock); RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */ put_uprobe(uprobe);