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Wed, 08 Jul 2026 07:39:16 +0000 Message-ID: <3e174563-e2c3-4fca-8a7c-3adf548e01f6@suse.de> Date: Wed, 8 Jul 2026 09:39:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 06/10] drm/i915: Implement vga_switcheroo_client_ops.pre_switch To: sashiko-reviews@lists.linux.dev Cc: dri-devel@lists.freedesktop.org References: <20260707135724.247562-1-tzimmermann@suse.de> <20260707135724.247562-7-tzimmermann@suse.de> <20260707141722.A6A0F1F00A3E@smtp.kernel.org> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: <20260707141722.A6A0F1F00A3E@smtp.kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: 1C8EA75AF8 X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_TLS_ALL(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email,suse.de:mid,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.com:url]; RCPT_COUNT_TWO(0.00)[2]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; TO_DN_NONE(0.00)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Am 07.07.26 um 16:17 schrieb sashiko-bot@kernel.org: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [High] AB-BA deadlock between `vgasr_mutex` and `dev->clientlist_mutex` during VGA switcheroo and DRM client hotplug/registration. > -- > > --- Patch [6]: [PATCH 06/10] drm/i915: Implement vga_switcheroo_client_ops.pre_switch --- > commit ca43d8e034e1ee27918b22e1b7a19b8f6a5b4a67 > Author: Thomas Zimmermann > > drm/i915: Implement vga_switcheroo_client_ops.pre_switch > > This commit implements the pre_switch callback for vga_switcheroo in the > i915 driver. It calls drm_client_dev_acquire_outputs() to push fbcon > updates from vga_switcheroo into DRM's fbdev emulation. > >> diff --git a/drivers/gpu/drm/i915/i915_switcheroo.c b/drivers/gpu/drm/i915/i915_switcheroo.c >> index 7e0791024282e..6b306ece0556a 100644 >> --- a/drivers/gpu/drm/i915/i915_switcheroo.c >> +++ b/drivers/gpu/drm/i915/i915_switcheroo.c > [ ... ] >> @@ -58,10 +59,19 @@ static bool i915_switcheroo_can_switch(struct pci_dev *pdev) >> atomic_read(&i915->drm.open_count) == 0; >> } >> >> +static void i915_switcheroo_pre_switch(struct pci_dev *pdev) >> +{ >> + struct drm_i915_private *i915 = pdev_to_i915(pdev); >> + >> + if (i915 && intel_display_device_present(i915->display)) >> + drm_client_dev_acquire_outputs(&i915->drm); > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > [Severity: High] > Does this code introduce an AB-BA deadlock between vgasr_mutex and > dev->clientlist_mutex? > > A GPU switch triggered via userspace will acquire vgasr_mutex and eventually > call this pre_switch callback: > > vga_switcheroo_debugfs_write() [acquires vgasr_mutex] > vga_switchto_stage2() > i915_switcheroo_pre_switch() > drm_client_dev_acquire_outputs() [acquires dev->clientlist_mutex] > > However, a DRM client hotplug event can acquire these locks in the reverse > order: > > drm_client_dev_hotplug() [acquires dev->clientlist_mutex] > drm_fbdev_client_hotplug() > register_framebuffer() > fbcon_fb_registered() > do_fb_registered() > vga_switcheroo_client_fb_set() [acquires vgasr_mutex] > > Could this lead to a system hang when a GPU switch races with a display > hotplug event? Patch 10 removes calls to vga_switcheroo_client_fb_set() entirely. I could try to reorganize the series to avoid the vulnerable intermediate states. > >> +} >> + >> static const struct vga_switcheroo_client_ops i915_switcheroo_ops = { >> .set_gpu_state = i915_switcheroo_set_state, >> .reprobe = NULL, -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)