From nobody Mon Feb 9 09:10:22 2026 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 F39A854F8C for ; Mon, 8 Jul 2024 09:29:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720430970; cv=none; b=jW7S1jRFVn+BoJmh4AAHdou8FmKs3eGei7jbatFta4JpYppYzdQToDW4I4Gu24Z24uydA0MX7BcaUb/GhHGCLncrn4FY1gIjU9ipw4PGG/+YXHo/yoboNHSGlYNg8sMdrC8eVZzGT+uFFXSX6dNpv6zXELrXQuHCTq14BNOqc1Y= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720430970; c=relaxed/simple; bh=Z+tf+zGbvC0gSaMaFf/2zXls1bdcxX+Z2+74bcL4sJ4=; h=Message-Id:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=kpoq2AN3XVlnEbl+wR0vUsyuBhf3dRg1ErKAcs3McDAQ/2W0GYQTnLd4VEIsfGPO1jowEl/mJSG87KqsoXmf4s55b5Gj4F3k0voJnaAoKD+3abPgL/EuCbDxXBjzeUBmpAF1FbHlrtkEq1KymgpFX2STwdDOPCD0aAOrxaCCd4E= 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=fLP2gPzh; arc=none smtp.client-ip=90.155.92.199 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="fLP2gPzh" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=FqzzvelQ00c0zN3R4blHkZc53U+LXab6OIi85Tl6cJg=; b=fLP2gPzh1ziLfREnPNinzFXPxf sBEqJ7n7OTCxUyDyP8q/bXvawVZAyjInEmcSc9+0lpU6nc+ksfETXaboPaCDQ9WWygKzm7IuFyF3c mdAtHCaTIB2pjKBQaFTfbbfX+WqW4HmpzkMfvoh3bay70f2GyIRbGmr46tGoMC7SQ3366a4UbzO5c E05PXU/Lb8eBJ+rM9uYp7juW0cnlXrPuBo3PN4QpeyNH1TAFBGx6Ubprnrw9AfyfCzxVno4myTp0i 0nsukPCI+l7AkUVhOjNh3ynw+0lDiDKXAcm+7kGKipX5FCQApa+iyIIjpDEntWqkhB7FTd2yAI73Y av1EunCQ==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sQkgN-00000000ZsP-4BCt; Mon, 08 Jul 2024 09:29:18 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 0) id 184B2302182; Mon, 8 Jul 2024 11:29:13 +0200 (CEST) Message-Id: <20240708092415.695619684@infradead.org> User-Agent: quilt/0.65 Date: Mon, 08 Jul 2024 11:12:46 +0200 From: Peter Zijlstra To: mingo@kernel.org, andrii@kernel.org Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, rostedt@goodmis.org, mhiramat@kernel.org, oleg@redhat.com, jolsa@kernel.org, clm@meta.com, paulmck@kernel.org Subject: [PATCH 05/10] perf/uprobe: SRCU-ify uprobe->consumer list References: <20240708091241.544262971@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" With handle_swbp() hitting concurrently on (all) CPUs the uprobe->register_rwsem can get very contended. Replace it with SRCU+mutex. Signed-off-by: Peter Zijlstra (Intel) --- kernel/events/uprobes.c | 37 +++++++++++++++++++++++-------------- 1 file changed, 23 insertions(+), 14 deletions(-) --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -26,6 +26,7 @@ #include #include #include +#include =20 #include =20 @@ -49,6 +50,8 @@ static struct mutex uprobes_mmap_mutex[U =20 DEFINE_STATIC_PERCPU_RWSEM(dup_mmap_sem); =20 +DEFINE_STATIC_SRCU(uprobes_srcu); + /* Have a copy of original instruction */ #define UPROBE_COPY_INSN 0 =20 @@ -56,7 +59,7 @@ 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 mutex register_mutex; struct rw_semaphore consumer_rwsem; struct list_head pending_list; struct uprobe_consumer *consumers; @@ -750,7 +753,7 @@ static struct uprobe *alloc_uprobe(struc uprobe->inode =3D inode; uprobe->offset =3D offset; uprobe->ref_ctr_offset =3D ref_ctr_offset; - init_rwsem(&uprobe->register_rwsem); + mutex_init(&uprobe->register_mutex); init_rwsem(&uprobe->consumer_rwsem); =20 /* add to uprobes_tree, sorted on inode:offset */ @@ -1129,10 +1132,12 @@ void uprobe_unregister(struct inode *ino if (WARN_ON(!uprobe)) return; =20 - down_write(&uprobe->register_rwsem); + mutex_lock(&uprobe->register_mutex); __uprobe_unregister(uprobe, uc); - up_write(&uprobe->register_rwsem); + mutex_unlock(&uprobe->register_mutex); put_uprobe(uprobe); + + synchronize_srcu(&uprobes_srcu); } EXPORT_SYMBOL_GPL(uprobe_unregister); =20 @@ -1192,7 +1197,7 @@ static int __uprobe_register(struct inod * We can race with uprobe_unregister()->delete_uprobe(). * Check uprobe_is_active() and retry if it is false. */ - down_write(&uprobe->register_rwsem); + mutex_lock(&uprobe->register_mutex); ret =3D -EAGAIN; if (likely(uprobe_is_active(uprobe))) { consumer_add(uprobe, uc); @@ -1200,7 +1205,7 @@ static int __uprobe_register(struct inod if (ret) __uprobe_unregister(uprobe, uc); } - up_write(&uprobe->register_rwsem); + mutex_unlock(&uprobe->register_mutex); put_uprobe(uprobe); =20 if (unlikely(ret =3D=3D -EAGAIN)) @@ -1240,12 +1245,12 @@ int uprobe_apply(struct inode *inode, lo if (WARN_ON(!uprobe)) return ret; =20 - down_write(&uprobe->register_rwsem); + mutex_lock(&uprobe->register_mutex); for (con =3D uprobe->consumers; con && con !=3D uc ; con =3D con->next) ; if (con) ret =3D register_for_each_vma(uprobe, add ? uc : NULL); - up_write(&uprobe->register_rwsem); + mutex_unlock(&uprobe->register_mutex); put_uprobe(uprobe); =20 return ret; @@ -2087,14 +2092,19 @@ static struct uprobe *find_active_uprobe return uprobe; } =20 +#define for_each_consumer_rcu(pos, head) \ + for (pos =3D rcu_dereference_raw(head); pos; \ + pos =3D rcu_dereference_raw(pos->next)) + static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) { struct uprobe_consumer *uc; int remove =3D UPROBE_HANDLER_REMOVE; bool need_prep =3D false; /* prepare return uprobe, when needed */ =20 - down_read(&uprobe->register_rwsem); - for (uc =3D uprobe->consumers; uc; uc =3D uc->next) { + guard(srcu)(&uprobes_srcu); + + for_each_consumer_rcu(uc, uprobe->consumers) { int rc =3D 0; =20 if (uc->handler) { @@ -2116,7 +2126,6 @@ static void handler_chain(struct uprobe WARN_ON(!uprobe_is_active(uprobe)); unapply_uprobe(uprobe, current->mm); } - up_read(&uprobe->register_rwsem); } =20 static void @@ -2125,12 +2134,12 @@ handle_uretprobe_chain(struct return_ins struct uprobe *uprobe =3D ri->uprobe; struct uprobe_consumer *uc; =20 - down_read(&uprobe->register_rwsem); - for (uc =3D uprobe->consumers; uc; uc =3D uc->next) { + guard(srcu)(&uprobes_srcu); + + for_each_consumer_rcu(uc, uprobe->consumers) { if (uc->ret_handler) uc->ret_handler(uc, ri->func, regs); } - up_read(&uprobe->register_rwsem); } =20 static struct return_instance *find_next_ret_chain(struct return_instance = *ri)