From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590193; b=0jvgqPpDCmWVyTfd/Jrhy/s1r3z1JPyzHmHLeFPTCvpvE4ZcJeioKiqVkKx1dVHtv72x DwF2ajStoGUv4v1MBUDrRsz6ctu2DScYJvzp7/4sl9XYCsm2oIWoSoQ6hWD60RoqyZMld 1NlqwHJ6KIQcLaeL5b93a3DZwIsasQTjxfFLe9uVZvF3n3N/qWlB8Xxs5/mbiMSoDtMsC Hl3N2vHkcX1D5Q7+u4v46nJqc/BTzfbtnTK7eU/35CN/rWoRwjaWaJxlbVJiiTYI8w0Cw XHuc/AyW6uoFiArK1CNmQEIVWy8IIpHzGeLTbKeNhjc0FdW0bpZyAM1utJDvBdgCOug== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590193; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=pqpopvVU0ib6SyiFSCjUdjg1Tu3dfCipVlnFFwrkFlU=; b=336PpzSHbIEpTKQBlxdH1Hqm49clPsDsNyy/fjXINxmvgsMjvtWYLsT4zruPh1VBWoXn aNcGldAnK7Aa1bX6DI1QpAilME5SXWX/YXipcirKv7VVZbkt2Fl2X0sLKzyW8n8DTK9aX Y9MVE2QlekoaNzW0mSdea4gBXmqr64OES+0iu3KIapAMprBr9UlCSsxrVbwkNUxTuiZ+j W3RWcAPSyFaZ9MHARXzcZccDSRfI1b3vnM6J5ptUlxUTNuscKm0zqkshx3F9SNqx1OiAp 9MnB8B+NW+i/jDVl/X6n9TI3C0RDhsrMEDdvlMzyoff97X4i9oWt2H2v/01uidLs+Ow== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=0vwiQTh0; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9F8EA606B36A; Fri, 13 Nov 2026 17:16:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=0vwiQTh0 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4C7DF1F000CB; Fri, 13 Nov 2026 17:16:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590193; bh=pqpopvVU0ib6SyiFSCjUdjg1Tu3dfCipVlnFFwrkFlU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=0vwiQTh0JuyvmAFQ4Vhh4fl4+iUmbKP4heGXfgl0Qltnei/6q/grnPdZTJaZhm6fI y4BUGE2ON4RqlnNan2XrVP8NF/lxulDaRmbDu+QLhZNUfT0tw0khEzk9BgTKz8EF5N uoPhNEcbuN69JMEEkVhyq0flkPV+VUMEb4a5SE1Q= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Iago Toral Quiroga , =?UTF-8?q?Ma=C3=ADra=20Canal?= , Sasha Levin Subject: [PATCH 6.18 201/686] drm/vc4: Publish the output fence outside of job_lock Date: Fri, 13 Nov 2026 10:45:34 -0500 Message-ID: <20261113153827.857460660@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Maíra Canal [ Upstream commit 9ee552a42c3905b4547e83173d46413137ec329a ] job_lock is taken by the V3D interrupt handler, so nesting an IRQ-unsafe lock under it creates an inversion. drm_syncobj_replace_fence() takes drm_syncobj::lock, which other paths acquire with interrupts enabled. For example, a thread interrupted while holding it blocks the handler on job_lock, and the handler can only make progress once the submit path releases job_lock, which it cannot do while waiting for drm_syncobj::lock. This is reported by lockdep: [ 188.139076] ======================================================== [ 188.139086] WARNING: possible irq lock inversion dependency detected [ 188.139096] 7.3.0-rc3-00067-gc4f3feeaf60f #67 Tainted: G C [ 188.139108] -------------------------------------------------------- [ 188.139116] swapper/0/0 just changed the state of lock: [ 188.139125] ffff0000054f8ff8 (&vc4->job_lock){-...}-{3:3}, at: vc4_irq+0xa8/0x28c [vc4] [ 188.139234] but this lock took another, HARDIRQ-unsafe lock in the past: [ 188.139242] (&syncobj->lock){+.+.}-{3:3} [ 188.139256] and interrupts could create inverse lock ordering between them. [ 188.139267] other info that might help us debug this: [ 188.139275] Possible interrupt unsafe locking scenario: [ 188.139284] CPU0 CPU1 [ 188.139291] ---- ---- [ 188.139299] lock(&syncobj->lock); [ 188.139312] local_irq_disable(); [ 188.139320] lock(&vc4->job_lock); [ 188.139335] lock(&syncobj->lock); [ 188.139350] [ 188.139358] lock(&vc4->job_lock); [ 188.139372] *** DEADLOCK *** Hand the fence over after job_lock is dropped. The job can complete and drop exec->fence in that window, so take a reference first and publish through the local pointer, as exec may already be gone. Cc: stable@vger.kernel.org Fixes: e84fcb95e074 ("drm/vc4: Export fence through syncobj") Reviewed-by: Iago Toral Quiroga Link: https://patch.msgid.link/20261004-vc4-misc-fixes-v1-1-b763df9e33e1@igalia.com Signed-off-by: Maíra Canal Signed-off-by: Sasha Levin --- drivers/gpu/drm/vc4/vc4_gem.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/vc4/vc4_gem.c b/drivers/gpu/drm/vc4/vc4_gem.c index 5eadf11f289a8..812636318cd9f 100644 --- a/drivers/gpu/drm/vc4/vc4_gem.c +++ b/drivers/gpu/drm/vc4/vc4_gem.c @@ -639,8 +639,11 @@ vc4_queue_submit(struct drm_device *dev, struct vc4_exec_info *exec, fence->seqno = exec->seqno; exec->fence = &fence->base; + /* The job can complete and drop exec->fence as soon as job_lock is + * released, so hold our own reference. + */ if (out_sync) - drm_syncobj_replace_fence(out_sync, exec->fence); + dma_fence_get(&fence->base); vc4_attach_fences(exec); @@ -662,6 +665,11 @@ vc4_queue_submit(struct drm_device *dev, struct vc4_exec_info *exec, spin_unlock_irqrestore(&vc4->job_lock, irqflags); + if (out_sync) { + drm_syncobj_replace_fence(out_sync, &fence->base); + dma_fence_put(&fence->base); + } + return 0; } -- 2.53.0