From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f48.google.com (mail-ej1-f48.google.com [209.85.218.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D2CC8417369 for ; Thu, 30 Jul 2026 11:38:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785411535; cv=none; b=pDn1B/PlpIgnfrTH8GZXP4avWNl5iUC5zUC+N1a7t0YfhqvHZM8AkXpd4WU2WOrTEzx/4uieuinIqC3dKQO27UQVdXCRRIqAjeuGlM/MMwZuQTxCxS6unuROr8JvjBWjGrela66TEAO8fMPX8hRJ/8VbjQVN6MGkbZTVZd8mbL0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785411535; c=relaxed/simple; bh=iHqcO2Rnwzd2L6OufeDd5pmiMKk3eaglPKa6bUr+zcM=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=R+cV1y1zHcLWFWZ8YdrwLaXZZ1u7Xolcdr/dsVuPoSfBPanZqjCNgn4k6DZD6/UPvi0HzpzoMN3nnW4mtb9XOz5TBELbL6p20S99nrk0oRn337Liqhd0ZdeKw0PAH1z88Y6xgKul1KUbr/QujYJ/PXczDZs5tyJwhndJg47/ziw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=jf9On7wZ; arc=none smtp.client-ip=209.85.218.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jf9On7wZ" Received: by mail-ej1-f48.google.com with SMTP id a640c23a62f3a-c1712a04ddaso335528966b.2 for ; Thu, 30 Jul 2026 04:38:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1785411532; x=1786016332; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:date:from:from:to:cc:subject :date:message-id:reply-to:content-type; bh=plwMvaUEY9e4Fyn22yn6zx4oz4Vgz2fcf+cgeq068e0=; b=jf9On7wZ7ubfCfF3H+VRwPMPf77nbTNmT2eFrx/RzP2STYTsNF3YlpqYDk/GzUmJWV 46ii+55bow6qfkVVGeDxLHTSbKowqf9VW1JVFHg3N0ZViQZqqGxX94iTElE2YMXHoQJP DhS8AUgdAkT3FcZ8o5aJrWqzWEm5TNTIJIuA/zij/oiMLIEx0pkd11DpUF/dRhviYClc JEyVE0ZYAOP51aFElNbGTPTPQ1VG12v+oZqI4q1cP3OhCS+v6QNspu2nLcGgTCg9zxdt rTeJfC8VkUHcdXTe0S0oHNVU/Q4DNkCHQgkexkHy9xYhqarjmHLjEmIPaY/+NF6BTSES Ce8A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785411532; x=1786016332; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:date:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=plwMvaUEY9e4Fyn22yn6zx4oz4Vgz2fcf+cgeq068e0=; b=G8FZgIpB/STYNUbz1SoQlUf3D/Uswxj/QdOU/wQdxsPIXo1Kl2XIPgxhKcPwmPT0ov DU9alK98AnpQUfewrdtNld+D6zk1FK7jSlcE/H4MF2VwQ1wkFDK26BL3GvgL1WdwvlaW M3sQzMKLSqDk27neSEaRVj259v9/lxllsyLwbC1FrSQ4B3j2+yv5NnP0VIhxd1O3TFAv 4LIJte+6cynlqpZ46+F70bF+XBuku16vrXjElWVqC+p88vXkv0vviXg6E1Y6JqCKiIgr 28ZB4Tyf4EXLB/9FvW+OddJ8n38P8iRNzxUvN46J2DBbdEZKsyfPE+4jROlTdgFuWI5A W3xw== X-Forwarded-Encrypted: i=1; AHgh+Rp5+UFRpksvNBn440Ok8ReQk08JhXhDp2fp5U1bPn48fwo+BgGzpnPhntEXkL42C/6E3hA=@vger.kernel.org X-Gm-Message-State: AOJu0YytFtZQ6w898jsS5Hfs7R2PvQiPsguMPXJJOLZlc7pmTsSRexV6 dmbJR/aXD5lttRmoLQWxxQ5bwkeSCacRV1/H8QoRW/ZB8QKK8EEbCEcd X-Gm-Gg: AR+sD12k2X0j4CzcMHNliX50+fEwzvkzfBoelkTmcrOFUgQ2xZwy5casNh96bpRaT/U 2Xoe2n6+pqyVSiRYZeYyeP/yrT1Euc3O0/15AKcoeIMFML0NdntIiWra/ggaJxexIxeI+rWv2lB +3U9oC9ML0yFclBzDACcLqZkgdR/d3qe4qSwz/GpjvVwpMlZUAoDAYQ4eLsKxtBV0y1EHosamwN 0ik/lVSC4FZO4BvE7tjY4fD+nqGdiPcgZVF2DMARDaUe3Q7ulGczrXZmCShTb5cIwK0Drek2RbM lcDqXQzxhlRrdYVQDvmsunlj7XjubLCEm96zg/uj5CxHHGtBpICjPSZbMUOtQvNM3tKW2NyWMDF Ci9f4u/TCvfUFxi9f5T86HB21u69AH3mUggM1yTaDfMS1RrhLOmaBnUIncMf/wLHxaj+WrPKSwM SVJnepEd/AqWfPvdAclcZBVABrMe5Tn5kJ7ywd71oib72HyZ8= X-Received: by 2002:a17:907:c1c:b0:c1f:983a:368c with SMTP id a640c23a62f3a-c1fa5753beemr105392866b.49.1785411531532; Thu, 30 Jul 2026 04:38:51 -0700 (PDT) Received: from krava ([173.38.220.35]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c1fa8b6da32sm57922366b.39.2026.07.30.04.38.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2026 04:38:51 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 30 Jul 2026 13:38:48 +0200 To: Leon Hwang Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , stable@vger.kernel.org, Tao Chen , bpf@vger.kernel.org, Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , Quentin Monnet , STAR Labs SG , Arnaud Lecomte Subject: Re: [PATCHv2 bpf-next 05/11] bpf: Disable preemption in bpf_get_stackid Message-ID: References: <20260729083807.1588544-1-jolsa@kernel.org> <20260729083807.1588544-6-jolsa@kernel.org> <78c72a5b-0db5-47da-8b35-e6a2e6976d7c@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <78c72a5b-0db5-47da-8b35-e6a2e6976d7c@linux.dev> On Wed, Jul 29, 2026 at 06:30:26PM +0800, Leon Hwang wrote: > On 29/7/26 16:38, Jiri Olsa wrote: > > The get_perf_callchain call needs disabled preemption plus we need > > it disabled as long as we access its returned trace entries buffer. > > > > Note the bpf_get_stackid_pe function is executed already with > > preemption disabled. > > > > Cc: stable@vger.kernel.org > > Fixes: d5a3b1f69186 ("bpf: introduce BPF_MAP_TYPE_STACK_TRACE") > > Reported-by: Tao Chen > > Closes: https://lore.kernel.org/bpf/20260206090653.1336687-2-chen.dylane@linux.dev/ > > Signed-off-by: Jiri Olsa > > --- > > kernel/bpf/stackmap.c | 19 +++++++++++++------ > > 1 file changed, 13 insertions(+), 6 deletions(-) > > > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > > index 43b1e5436047..e48ddb4edd47 100644 > > --- a/kernel/bpf/stackmap.c > > +++ b/kernel/bpf/stackmap.c > > @@ -624,30 +624,37 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, > > struct perf_callchain_entry *trace; > > struct stackid stackid; > > bool kernel = !user; > > + int err = -EFAULT; > > u32 max_depth; > > - int err; > > > > if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | > > BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) > > return -EINVAL; > > > > max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags); > > + > > + preempt_disable(); > > Better to use the guard-style guard(preempt)() in this series. we prefer to call stackid_install with preemption enabled jirka > > Thanks, > Leon > > > trace = get_perf_callchain(regs, kernel, user, max_depth, > > false, false, 0); > > > > if (unlikely(!trace)) > > /* couldn't fetch the stack trace */ > > - return -EFAULT; > > + goto out; > > > > err = stackid_fastpath(&stackid, map, trace, flags); > > if (err != -ENOENT) > > - return err; > > + goto out; > > > > new_bucket = stackid_new_bucket(&stackid, map); > > - if (!new_bucket) > > - return -ENOMEM; > > + if (new_bucket) { > > + preempt_enable(); > > + return stackid_install(&stackid, map, new_bucket, flags); > > + } > > + err = -ENOMEM; > > > > - return stackid_install(&stackid, map, new_bucket, flags); > > +out: > > + preempt_enable(); > > + return err; > > } > > > > const struct bpf_func_proto bpf_get_stackid_proto = { >