From nobody Tue Nov 26 00:51:17 2024 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 952A3155308; Thu, 24 Oct 2024 04:42:06 +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=1729744926; cv=none; b=LSe17if4S5u/mXzZdm3zvU9tgfrD0SRnNH5yZOzRWiMFFQlHSdchN9DJcaTkNL5V2UmkEbuNkg8gblAwlk9NK8CrB6EbIn1b6M8nS/bkI9btmc3WubwmcthQ3QmqYxd/DDcrERtLfzgPDqihb1nGoNEXIsMGBeLp7BnQgPC7AaI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729744926; c=relaxed/simple; bh=qxdeLmS88RTlcJ2/gkJB2e6Py7R8rZS7YIxGfYTXtUU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XHGJySIIEZl99WmgZ7VBKKjEJQfHSUM+BFdJ6CAm2zgN7uophVe/AnXLE0QWsxPAbbxySMB7nghv0BbTMvuWHxyATHiWsRsKrCme7Lrcyrej97KoNdKFyUWTYDKRGbd84qq2ge9DKxtrLwnibKeYPOC0PEGZUQhSQ8oNpqGvs54= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KUFJ5KJR; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KUFJ5KJR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E048CC4CEC7; Thu, 24 Oct 2024 04:42:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729744926; bh=qxdeLmS88RTlcJ2/gkJB2e6Py7R8rZS7YIxGfYTXtUU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KUFJ5KJRLyqhjeIARG9R4XTt/gp6Qi9eLME3jYX30jUzd0DVMUOBDgKKe0Gi9HLTu cPDjwHTGxoxOnLu0Edr9qlPgA/VC7d7J6IzdDGErUUfsfO5hOq6dFk+QirNDOofPQZ dyeArngbb1v5L+TmhVCm+iCnraOSxB/ZwUIbbbLeHJAD0hGYvxBWFqN+Nx+29IoZ4I 9aQUYX6BPJZ8KCGkl3rJbvPEfMf1MnRFfoBdv3KM41HcTHWSHv2LeODxdo/7j255j+ 5jWqyGGUYEkCFvi2Hfkuqn1CPB5zItRDGl5Fc5AOJGD7w0ZBmxGlAMjQ8O0Mx94nQb eu7Wx0ngh0QPw== From: Andrii Nakryiko To: linux-trace-kernel@vger.kernel.org, peterz@infradead.org, oleg@redhat.com Cc: rostedt@goodmis.org, mhiramat@kernel.org, mingo@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, Andrii Nakryiko Subject: [PATCH v3 tip/perf/core 1/2] uprobes: allow put_uprobe() from non-sleepable softirq context Date: Wed, 23 Oct 2024 21:41:58 -0700 Message-ID: <20241024044159.3156646-2-andrii@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20241024044159.3156646-1-andrii@kernel.org> References: <20241024044159.3156646-1-andrii@kernel.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" Currently put_uprobe() might trigger mutex_lock()/mutex_unlock(), which makes it unsuitable to be called from more restricted context like softirq. Let's make put_uprobe() agnostic to the context in which it is called, and use work queue to defer the mutex-protected clean up steps. RB tree removal step is also moved into work-deferred callback to avoid potential deadlock between softirq-based timer callback, added in the next patch, and the rest of uprobe code. We can rework locking altogher as a follow up, but that's significantly more tricky, so warrants its own patch set. For now, we need to make sure that changes in the next patch that add timer thread work correctly with existing approach, while concentrating on SRCU + timeout logic. Signed-off-by: Andrii Nakryiko --- kernel/events/uprobes.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 4ef4b51776eb..d7e489246608 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -27,6 +27,7 @@ #include #include #include +#include =20 #include =20 @@ -61,7 +62,10 @@ struct uprobe { struct list_head pending_list; struct list_head consumers; struct inode *inode; /* Also hold a ref to inode */ - struct rcu_head rcu; + union { + struct rcu_head rcu; + struct work_struct work; + }; loff_t offset; loff_t ref_ctr_offset; unsigned long flags; /* "unsigned long" so bitops work */ @@ -625,10 +629,9 @@ static void uprobe_free_rcu(struct rcu_head *rcu) kfree(uprobe); } =20 -static void put_uprobe(struct uprobe *uprobe) +static void uprobe_free_deferred(struct work_struct *work) { - if (!refcount_dec_and_test(&uprobe->ref)) - return; + struct uprobe *uprobe =3D container_of(work, struct uprobe, work); =20 write_lock(&uprobes_treelock); =20 @@ -652,6 +655,15 @@ static void put_uprobe(struct uprobe *uprobe) call_rcu_tasks_trace(&uprobe->rcu, uprobe_free_rcu); } =20 +static void put_uprobe(struct uprobe *uprobe) +{ + if (!refcount_dec_and_test(&uprobe->ref)) + return; + + INIT_WORK(&uprobe->work, uprobe_free_deferred); + schedule_work(&uprobe->work); +} + static __always_inline int uprobe_cmp(const struct inode *l_inode, const loff_t l_offset, const struct uprobe *r) --=20 2.43.5