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(unknown [36.110.52.3]) by APP-03 (Coremail) with SMTP id rQCowACXpMsI2RZqbNWNEg--.9811S2; Wed, 27 May 2026 19:44:08 +0800 (CST) From: Jiakai Xu To: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= , David Airlie , Maarten Lankhorst , Maxime Ripard , Simona Vetter , Thomas Zimmermann , Jiakai Xu Subject: [PATCH] drm/atomic-helper: Downgrade vblank wait timeout from WARN to drm_warn Date: Wed, 27 May 2026 11:43:55 +0000 Message-Id: <20260527114355.3681305-1-xujiakai24@mails.ucas.ac.cn> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: rQCowACXpMsI2RZqbNWNEg--.9811S2 X-Coremail-Antispam: 1UD129KBjvJXoW3GFykury7Gry3ArWkKFWkCrg_yoW7Wry3pr 4agr9Fkr48Xan8ta9rJ3WxA343Ka17Aa4xt397Jw1fZ3WUAFnrZrnrKrWFq34UJr1UZr4x tFnrAwnYkr1DCaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvC14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26r4j6ryUM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4j 6F4UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s 0DM2vYz4IE04k24VAvwVAKI4IrM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI 64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVW8JVWxJw Am72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lF7I21c0EjII2zVCS5cI20VAG YxC7MxkF7I0En4kS14v26r1q6r43MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r 1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CE b7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0x vE2Ix0cI8IcVCY1x0267AKxVWUJVW8JwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAI cVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2Kf nxnUUI43ZEXa7VUjEoGDUUUUU== X-CM-SenderInfo: 50xmxthndljko6pdxz3voxutnvoduhdfq/ When the system is under severe CPU pressure (e.g., SOFTLOCKUP), the hrtimer-based vblank simulation used by virtual GPU drivers like virtio-gpu may not fire within the 1000ms timeout. This triggers a WARN that, when panic_on_warn is set, panics the kernel unnecessarily. The timeout is not a kernel logic bug =E2=80=94 it is a transient system re= source condition. drm_atomic_helper_wait_for_flip_done() already uses drm_err() for a similar timeout, so downgrade this WARN to drm_warn() for consistency and to prevent secondary crashes under system stress. Fixes: 8d4d0d700dda ("drm/atomic-helper: Print an error if vblank wait time= s out") Signed-off-by: Jiakai Xu --- drivers/gpu/drm/drm_atomic_helper.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atom= ic_helper.c index 51f39edc31ed..7cad7aa4dd2e 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -1918,8 +1918,9 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device = *dev, drm_crtc_vblank_count(crtc), msecs_to_jiffies(1000)); =20 - WARN(!ret, "[CRTC:%d:%s] vblank wait timed out\n", - crtc->base.id, crtc->name); + if (!ret) + drm_warn(dev, "[CRTC:%d:%s] vblank wait timed out\n", + crtc->base.id, crtc->name); =20 drm_crtc_vblank_put(crtc); } --=20 2.34.1 Found by fuzzing. Here is the report: ------------[ cut here ]------------ [CRTC:35:crtc-0] vblank wait timed out WARNING: drivers/gpu/drm/drm_atomic_helper.c:1922 at drm_atomic_helper_wait= _for_vblanks+0x39a/0x3f0 home/zzzrrll/tmp/linux-7.0.10/drivers/gpu/drm/drm_= atomic_helper.c:1921, CPU#0: kworker/0:0/80597 Modules linked in: CPU: 0 UID: 0 PID: 80597 Comm: kworker/0:0 Tainted: G L 7.= 0.10 #2 PREEMPT(full)=20 Tainted: [L]=3DSOFTLOCKUP Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/= 2014 Workqueue: events drm_fb_helper_damage_work RIP: 0010:drm_atomic_helper_wait_for_vblanks+0x3a5/0x3f0 home/zzzrrll/tmp/l= inux-7.0.10/drivers/gpu/drm/drm_atomic_helper.c:1921 Code: f0 02 00 00 48 39 c5 7d 28 e8 47 7f 6c fe e9 b2 fd ff ff e8 3d 7f 6c = fe 48 8d 3d 56 41 7f 04 41 8b 75 60 4c 89 eb 49 8b 55 20 <67> 48 0f b9 3a e= b b3 e8 1f 7f 6c fe eb 05 e8 18 7f 6c fe 48 8d 05 RSP: 0018:ffa000000e817b40 EFLAGS: 00010293 RAX: ffffffff82faa093 RBX: ff1100000d5cebc8 RCX: ff11000018d39840 RDX: ff1100000d2ca830 RSI: 0000000000000023 RDI: ffffffff8779e1f0 RBP: 0000000000000000 R08: ffffffff82faa052 R09: 0000027b3c832418 R10: 0000027b3c832418 R11: 0000000000000000 R12: ff1100000a8f3230 R13: ff1100000d5cebc8 R14: ff11000018207300 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ff110000f40c5000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000071ad60 CR3: 0000000060bac000 CR4: 0000000000751ef0 PKRU: 55555554 Call Trace: drm_atomic_helper_commit_tail+0x132/0x1e0 home/zzzrrll/tmp/linux-7.0.10/dr= ivers/gpu/drm/drm_atomic_helper.c:1997 commit_tail+0x11d/0x210 home/zzzrrll/tmp/linux-7.0.10/drivers/gpu/drm/drm_= atomic_helper.c:2074 drm_atomic_helper_commit+0x3d5/0x3e0 home/zzzrrll/tmp/linux-7.0.10/drivers= /gpu/drm/drm_atomic_helper.c:2312 drm_atomic_commit+0x148/0x170 home/zzzrrll/tmp/linux-7.0.10/drivers/gpu/dr= m/drm_atomic.c:1782 drm_atomic_helper_dirtyfb+0x32b/0x440 home/zzzrrll/tmp/linux-7.0.10/driver= s/gpu/drm/drm_damage_helper.c:183 drm_fbdev_shmem_helper_fb_dirty+0x6f/0x120 home/zzzrrll/tmp/linux-7.0.10/d= rivers/gpu/drm/drm_fbdev_shmem.c:117 drm_fb_helper_fb_dirty home/zzzrrll/tmp/linux-7.0.10/drivers/gpu/drm/drm_f= b_helper.c:248 [inline] drm_fb_helper_damage_work+0xcf/0x1e0 home/zzzrrll/tmp/linux-7.0.10/drivers= /gpu/drm/drm_fb_helper.c:274 process_one_work home/zzzrrll/tmp/linux-7.0.10/kernel/workqueue.c:3289 [in= line] process_scheduled_works+0x2f8/0x6b0 home/zzzrrll/tmp/linux-7.0.10/kernel/w= orkqueue.c:3372 worker_thread+0x318/0x480 home/zzzrrll/tmp/linux-7.0.10/kernel/workqueue.c= :3453 kthread+0x18d/0x1e0 home/zzzrrll/tmp/linux-7.0.10/kernel/kthread.c:436 ret_from_fork+0x19f/0x480 home/zzzrrll/tmp/linux-7.0.10/arch/x86/kernel/pr= ocess.c:158 ret_from_fork_asm+0x1a/0x30 home/zzzrrll/tmp/linux-7.0.10/arch/x86/entry/e= ntry_64.S:245 ---[ end trace 0000000000000000 ]--- ---------------- Code disassembly (best guess), 2 bytes skipped: 0: 00 00 add %al,(%rax) 2: 48 39 c5 cmp %rax,%rbp 5: 7d 28 jge 0x2f 7: e8 47 7f 6c fe call 0xfe6c7f53 c: e9 b2 fd ff ff jmp 0xfffffdc3 11: e8 3d 7f 6c fe call 0xfe6c7f53 16: 48 8d 3d 56 41 7f 04 lea 0x47f4156(%rip),%rdi # 0x47f4173 1d: 41 8b 75 60 mov 0x60(%r13),%esi 21: 4c 89 eb mov %r13,%rbx 24: 49 8b 55 20 mov 0x20(%r13),%rdx * 28: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2d: eb b3 jmp 0xffffffe2 2f: e8 1f 7f 6c fe call 0xfe6c7f53 34: eb 05 jmp 0x3b 36: e8 18 7f 6c fe call 0xfe6c7f53 3b: 48 rex.W 3c: 8d .byte 0x8d 3d: 05 .byte 0x5