From nobody Thu Apr 9 13:38:31 2026 Received: from mail-yw1-f172.google.com (mail-yw1-f172.google.com [209.85.128.172]) (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 229441862 for ; Mon, 9 Mar 2026 00:10:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773015055; cv=none; b=WmHOeBe8h4k4DU9ESN39rSfbJUJF5ItDjuQT+vsLb/jmBFCEU5Pb1cRfNxc87B3+hyPjD0E/mnG4nzaF2KVTl7+LPlkD5Bz0uUp7oKeQRdaSQBquPojzUYwTgvT4h954J9UELKC9+fzj1KCu97S6O5CutSI36ikEOeQC4+E/xV4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773015055; c=relaxed/simple; bh=pXEEhVHwuVgT/fu21TaSjJ5tO5mqGtan/ccC2ML+GCU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=lJF5MgBYRkaekZeRp6yDoF2THTIYyyRgZXlT2VFKGh83CdF+meCsHbwLZQIyBos0HYtLfEUKrN0ezqz0eaBszRagGp4mkI4mA72PMt16qBlqcKdoobHGs/pCiC05Xk83lHUx5/giXNKqb2H2pqwWzq4l70U9LULZ/hwjLveAw/g= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=sung-woo.kim; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.128.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=sung-woo.kim Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-yw1-f172.google.com with SMTP id 00721157ae682-79801df3e42so141562227b3.0 for ; Sun, 08 Mar 2026 17:10:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773015053; x=1773619853; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=bGAMFu2DWaW1aHTsL/PoCzheLXQYvpCKBh0Ov44tQ/U=; b=kNNqLBrogX/bAXDrh4x6VIkOxN182mXCS342FsesgbopI1gPih5sAxLULwaOiiAYoP h7tzQirvSvBGevpB+V1DQcGaZSiU43et/CCKlSi5Ss1K8aR+j8uetu+QGUemz3rh2vxb 74PbS1Dvh/KseYu/hEgt0oVC0UJWcSGL5AcfpeqcAxCUw+siGjwnHj5yfrspES5z8TF5 ZHW3/CWNv/NRCRzkIJgvbWqfdmLTQSGCVKv1OM9Ax7VZ2Dr4X5Z5SL03TfWiNBDvcmGx BrSnm34D7YkJQbzavx8YmVPtErFeL05usUDMdPE7N4fAGbK7Q9+2e5gbL9qWXPdrAmAN JleA== X-Forwarded-Encrypted: i=1; AJvYcCXu8YpygQq5T6wZvoWXQ3jGRdnPKArZAAImoMfoZZd8Ug/BL17K+Q4CtdITL8xXmNSYO0GArwhAUxCIY1c=@vger.kernel.org X-Gm-Message-State: AOJu0Yx7deY+HqinjeVlDXQW0q8eMTm8lJZfyV79OoCxkC4DWYZ3JzQ8 UDsLP9RmkPsy5kME70i/FC/A5O8MtkB6WVcGPKeS+LlegEif+gcI3Ee/ X-Gm-Gg: ATEYQzxbAAciYUc1Cph32xBDe0Fw5cIIff28J4ltMQXIhwANykh98l4XQB3+zz7ctPG 2QXxqXjZqGxtCRjzYvBvXsqPXTgsEZkkgSdNz3JmEo8hEzvflzCKpg60dFxSyQ/mxmDLm4ICyfK v2FcH0hJHHkn7Sl9H9XIDV2aOzfZFilwu1zWLO+W6+qWt8NPSfQSOicV8W68t4YjiyxxSJo0Y8w c4eNEMAcgahdny1EPmZMHX6Y7mJUSoIo4dVwU3iE2m3FynxuuCDn9KU2gKRTb7jYcR6cTwzfWB0 zBSljeaOn5wDm3mUXkyoHI9JAGDDf9YjPUw+mFgxqtHeCWq6NoK9a2PIXS+xUPhWhOOUOJ+Zkxq +aH00bUltSatkb8cmAr3bSnjbq81UrOlafzk0MLL5VEUB2HzcQV0DiNfWduWyERYABUJxyQl+F3 ILANpD5MffWw== X-Received: by 2002:a05:690c:6983:b0:798:1637:ff29 with SMTP id 00721157ae682-798dd77fc95mr89858247b3.17.1773015053125; Sun, 08 Mar 2026 17:10:53 -0700 (PDT) Received: from tofu.. ([128.210.0.165]) by smtp.googlemail.com with ESMTPSA id 00721157ae682-798dee89fe0sm37890847b3.47.2026.03.08.17.10.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Mar 2026 17:10:52 -0700 (PDT) From: Sungwoo Kim To: Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Alison Schofield , Vishal Verma , Ira Weiny , Dan Williams , Ben Widawsky Cc: Dave Tian , Sungwoo Kim , Jonathan Cameron , linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] cxl/hdm: fix a warning in devm_remove_action() Date: Sun, 8 Mar 2026 20:08:10 -0400 Message-ID: <20260309000810.2632065-2-iam@sung-woo.kim> X-Mailer: git-send-email 2.47.3 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" In the following race scenario, devm_remove_action() can be called before devm_add_action(), triggering a warning because there is no action to remove. To fix this, extend a critical section to embrace both __cxl_dpa_reserve() and devm_add_action(). task 1: cxl_dpa_alloc() __cxl_dpa_reserve() ...(1) devm_add_action() ...(4) task 2: cxl_dpa_free() guard() if (!cxled->dpa_res) ...(2) pass, due to (1) return 0; devm_cxl_dpa_release() devm_remove_action() ...(3) warning, no action is added yet Warning log: WARNING: ./include/linux/device/devres.h:160 at devm_remove_action include/= linux/device/devres.h:160 [inline], CPU#0: syz.1.6464/25993 WARNING: ./include/linux/device/devres.h:160 at devm_cxl_dpa_release driver= s/cxl/core/hdm.c:290 [inline], CPU#0: syz.1.6464/25993 WARNING: ./include/linux/device/devres.h:160 at cxl_dpa_free+0x2a4/0x320 dr= ivers/cxl/core/hdm.c:572, CPU#0: syz.1.6464/25993 Modules linked in: CPU: 0 UID: 0 PID: 25993 Comm: syz.1.6464 Not tainted 6.19.0-g15a37b05f387 = #10 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52c= a86e094d-prebuilt.qemu.org 04/01/2014 RIP: 0010:devm_remove_action include/linux/device/devres.h:160 [inline] RIP: 0010:devm_cxl_dpa_release drivers/cxl/core/hdm.c:290 [inline] RIP: 0010:cxl_dpa_free+0x2a4/0x320 drivers/cxl/core/hdm.c:572 Code: 01 31 ff 41 89 c4 89 c6 e8 a9 91 1d fe 45 85 e4 0f 85 55 ff ff ff e8 = 4b 96 1d fe 90 0f 0b 90 e9 47 ff ff ff e8 3d 96 1d fe 90 <0f> 0b 90 e9 63 f= f ff ff bb f0 ff ff ff e9 68 ff ff ff 48 c7 c7 f4 RSP: 0018:ffff888129f77bb8 EFLAGS: 00010282 RAX: 00000000000000f3 RBX: ffff888102f64000 RCX: ffffffff837301d3 RDX: 0000000000080000 RSI: ffffc90001c5a000 RDI: 0000000000000005 RBP: 00000000fffffffe R08: 0000000000000001 R09: ffff888123f98000 R10: 00000000fffffffe R11: 0000000000000000 R12: 0000000000000001 R13: ffff888102f64040 R14: dffffc0000000000 R15: ffff888102f64000 FS: 00007fae0488d6c0(0000) GS:ffff88827086d000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000012f7d6003 CR4: 0000000000770ef0 PKRU: 80000000 Call Trace: dpa_size_store+0xfb/0x230 drivers/cxl/core/port.c:269 dev_attr_store+0x58/0x80 drivers/base/core.c:2437 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142 kernfs_fop_write_iter+0x3d6/0x5d0 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x68e/0x1050 fs/read_write.c:688 ksys_write+0x12a/0x250 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfc/0x670 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fae0399c669 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 = 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff f= f 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fae0488d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fae03c15fa0 RCX: 00007fae0399c669 RDX: 000000000000000a RSI: 00002000000001c0 RDI: 0000000000000009 RBP: 00007fae03a32c71 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fae03c16038 R14: 00007fae03c15fa0 R15: 00007ffe53519fb8 irq event stamp: 1021 hardirqs last enabled at (1029): [] __up_console_sem+0x7= b/0x90 kernel/printk/printk.c:347 hardirqs last disabled at (1038): [] __up_console_sem+0x6= 0/0x90 kernel/printk/printk.c:345 softirqs last enabled at (1016): [] __do_softirq kernel/= softirq.c:656 [inline] softirqs last enabled at (1016): [] invoke_softirq kerne= l/softirq.c:496 [inline] softirqs last enabled at (1016): [] __irq_exit_rcu+0xb3/= 0xe0 kernel/softirq.c:723 softirqs last disabled at (1005): [] __do_softirq kernel/= softirq.c:656 [inline] softirqs last disabled at (1005): [] invoke_softirq kerne= l/softirq.c:496 [inline] softirqs last disabled at (1005): [] __irq_exit_rcu+0xb3/= 0xe0 kernel/softirq.c:723 Fixes: cf880423b6a0 ("cxl/hdm: Add support for allocating DPA to an endpoin= t decoder") Fixes: 9c57cde0dcbd ("cxl/hdm: Enumerate allocated DPA") Signed-off-by: Sungwoo Kim Reviewed-by: Dave Jiang Reviewed-by: Ira Weiny --- drivers/cxl/core/hdm.c | 34 +++++++++++++++++++++++++++++----- 1 file changed, 29 insertions(+), 5 deletions(-) diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c index e3f0c39e68124..86239b1790a31 100644 --- a/drivers/cxl/core/hdm.c +++ b/drivers/cxl/core/hdm.c @@ -509,13 +509,20 @@ int devm_cxl_dpa_reserve(struct cxl_endpoint_decoder = *cxled, struct cxl_port *port =3D cxled_to_port(cxled); int rc; =20 - scoped_guard(rwsem_write, &cxl_rwsem.dpa) - rc =3D __cxl_dpa_reserve(cxled, base, len, skipped); + guard(rwsem_write)(&cxl_rwsem.dpa); + rc =3D __cxl_dpa_reserve(cxled, base, len, skipped); =20 if (rc) return rc; =20 - return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled); + /* See comments in cxl_dpa_alloc()*/ + rc =3D devm_add_action(&port->dev, cxl_dpa_release, cxled); + if (rc) { + __cxl_dpa_release(cxled); + return rc; + } + + return 0; } EXPORT_SYMBOL_NS_GPL(devm_cxl_dpa_reserve, "CXL"); =20 @@ -613,7 +620,7 @@ static int __cxl_dpa_alloc(struct cxl_endpoint_decoder = *cxled, u64 size) struct resource *p, *last; int part; =20 - guard(rwsem_write)(&cxl_rwsem.dpa); + lockdep_assert_held_write(&cxl_rwsem.dpa); if (cxled->cxld.region) { dev_dbg(dev, "decoder attached to %s\n", dev_name(&cxled->cxld.region->dev)); @@ -679,11 +686,28 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled,= u64 size) struct cxl_port *port =3D cxled_to_port(cxled); int rc; =20 + guard(rwsem_write)(&cxl_rwsem.dpa); rc =3D __cxl_dpa_alloc(cxled, size); if (rc) return rc; =20 - return devm_add_action_or_reset(&port->dev, cxl_dpa_release, cxled); + /* + * Add the devres action while still holding cxl_rwsem.dpa to prevent + * a race with cxl_dpa_free(). Without this, a concurrent cxl_dpa_free() + * can observe dpa_res set (by __cxl_dpa_reserve()) and attempt + * devm_remove_action() before devm_add_action() has been called, + * triggering a WARN_ON in devm_remove_action(). + * Also, devm_add_action_or_reset() cannot be used here because + * cxl_dpa_release() tries to hold the dpa lock that is already held, + * causing a self deadlock. + */ + rc =3D devm_add_action(&port->dev, cxl_dpa_release, cxled); + if (rc) { + __cxl_dpa_release(cxled); + return rc; + } + + return 0; } =20 static void cxld_set_interleave(struct cxl_decoder *cxld, u32 *ctrl) --=20 2.47.3