From patchwork Thu Feb 20 04:22:59 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hou Tao X-Patchwork-Id: 13983293 X-Patchwork-Delegate: bpf@iogearbox.net Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 BFB9419D067 for ; Thu, 20 Feb 2025 04:10:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740024661; cv=none; b=bGUfd5FXv/8d2cgtXuUOsYrq14qC+zNIm7Jm+bl6M241OA39K+wcE9oUY5MYLxf7S2pi4GcbeHjg1zjdcrF0S997RmB0iFkk5I09UBA8szrvtE9Ysapr66pUHwKu/KQVzR4vG/JuCNeEcNXinSb05AXrpJsH1DdQtA/vu2+NjYk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740024661; c=relaxed/simple; bh=rAJiTr9LHB3H8hKcZBMz7Cb3QtUgY5mKRbovgIi5l+I=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=IdSiWpe0EKQ7miMaAyR7Li9p4OLQ+j3c0w6IoDSolzssk18L6AILcQDFqgbD12E+d0kT6duxolbCTSwNXuJO8vaJR9VycCzzs3ZO73E22Y+nBNwS3aWNVk6Zr3OO8baUm62ZGOSRzYIqCMgmD11j09ihqfGkF1ZyGutsaEq0SmU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4Yz0DF2xXlz4f3jt4 for ; Thu, 20 Feb 2025 12:10:37 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id B69701A0194 for ; Thu, 20 Feb 2025 12:10:53 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.124.27]) by APP4 (Coremail) with SMTP id gCh0CgDXOl9Jq7ZnxgNtEQ--.52521S4; Thu, 20 Feb 2025 12:10:51 +0800 (CST) From: Hou Tao To: bpf@vger.kernel.org Cc: Martin KaFai Lau , Alexei Starovoitov , Andrii Nakryiko , Eduard Zingerman , Song Liu , Hao Luo , Yonghong Song , Daniel Borkmann , KP Singh , Stanislav Fomichev , Jiri Olsa , John Fastabend , Puranjay Mohan , houtao1@huawei.com, xukuohai@huawei.com Subject: [PATCH bpf] bpf: Use preempt_count() directly in bpf_send_signal_common() Date: Thu, 20 Feb 2025 12:22:59 +0800 Message-Id: <20250220042259.1583319-1-houtao@huaweicloud.com> X-Mailer: git-send-email 2.29.2 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: gCh0CgDXOl9Jq7ZnxgNtEQ--.52521S4 X-Coremail-Antispam: 1UD129KBjvJXoW7KFyxXw4xKryxuFW8XFy8AFb_yoW8WF45pF 4xXr92kFWxJa1Yqw4jyw4kWFyUAan8X397GFnxGw4fJr4DXr4rWrsFgr42qF4Fgr9xXr93 Zrn29rW0vw48u3DanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvFb4IE77IF4wAFF20E14v26ryj6rWUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Cr0_Gr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I 0E14v26rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40E x7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x 0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1lc7CjxVAa w2AFwI0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxV Aqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r4a 6rW5MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6x kF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AK xVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvj xUFku4UUUUU X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-Patchwork-Delegate: bpf@iogearbox.net From: Hou Tao bpf_send_signal_common() uses preemptible() to check whether or not the current context is preemptible. If it is preemptible, it will use irq_work to send the signal asynchronously instead of trying to hold a spin-lock, because spin-lock is sleepable under PREEMPT_RT. However, preemptible() depends on CONFIG_PREEMPT_COUNT. When CONFIG_PREEMPT_COUNT is turned off (e.g., CONFIG_PREEMPT_VOLUNTARY=y), !preemptible() will be evaluated as 1 and bpf_send_signal_common() will use irq_work unconditionally. Fix it by unfolding "!preemptible()" and using "preempt_count() != 0 || irqs_disabled()" instead. Fixes: 87c544108b61 ("bpf: Send signals asynchronously if !preemptible") Signed-off-by: Hou Tao --- Hi, I had reported the problem at [1], however, it seems it got lost or was ignored. Therefore, I sent it out myself. [1]: https://lore.kernel.org/all/94fcfa71-51c1-2130-3452-ec58aaef94d0@huaweicloud.com/ kernel/trace/bpf_trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 71c1c02ca7a3e..2e6b525904d31 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -842,7 +842,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type, struct task_struc if (unlikely(is_global_init(task))) return -EPERM; - if (!preemptible()) { + if (preempt_count() != 0 || irqs_disabled()) { /* Do an early check on signal validity. Otherwise, * the error is lost in deferred irq_work. */