Hi Tomas, I think the issue could be possibly caused by the following, Please correct me if I'm wrong. drm_fb_helper_single_fb_probe() can fail with "Cannot find any crtc or sizes" which will cause fb_helper->funcs->fb_probe not being called, thus fb_helper->buffer remains NULL -- Since there could be the case that the fb_probe is never called, a subsequent modprobe -r will cause the following drm_client_buffer_vunmap(NULL) in drm_fbdev_cleanup() Best, - Tong On Mon, Mar 1, 2021 at 3:26 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote: > > Hi > > Am 28.02.21 um 05:46 schrieb Tong Zhang: > > drm_fbdev_cleanup() can be called when fb_helper->buffer is null, hence > > fb_helper->buffer should be checked before calling > > drm_client_buffer_vunmap(). This buffer is also checked in > > drm_client_framebuffer_delete(), so we should also do the same thing for > > drm_client_buffer_vunmap(). > > I think a lot of drivers are affected by this problem; probably most of > the ones that use the generic fbdev code. How did you produce the error? > > What I'm more concerned about is why the buffer is NULL. Was ther eno > hotplug event? Do you have a display attached? > > Best regards > Thomas > > > > > > [ 199.128742] RIP: 0010:drm_client_buffer_vunmap+0xd/0x20 > > [ 199.129031] Code: 43 18 48 8b 53 20 49 89 45 00 49 89 55 08 5b 44 89 e0 41 5c 41 5d 41 5e 5d > > c3 0f 1f 00 53 48 89 fb 48 8d 7f 10 e8 73 7d a1 ff <48> 8b 7b 10 48 8d 73 18 5b e9 75 53 fc ff 0 > > f 1f 44 00 00 48 b8 00 > > [ 199.130041] RSP: 0018:ffff888103f3fc88 EFLAGS: 00010282 > > [ 199.130329] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff8214d46d > > [ 199.130733] RDX: 1ffffffff079c6b9 RSI: 0000000000000246 RDI: ffffffff83ce35c8 > > [ 199.131119] RBP: ffff888103d25458 R08: 0000000000000001 R09: fffffbfff0791761 > > [ 199.131505] R10: ffffffff83c8bb07 R11: fffffbfff0791760 R12: 0000000000000000 > > [ 199.131891] R13: ffff888103d25468 R14: ffff888103d25418 R15: ffff888103f18120 > > [ 199.132277] FS: 00007f36fdcbb6a0(0000) GS:ffff88815b400000(0000) knlGS:0000000000000000 > > [ 199.132721] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 199.133033] CR2: 0000000000000010 CR3: 0000000103d26000 CR4: 00000000000006f0 > > [ 199.133420] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > [ 199.133807] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > [ 199.134195] Call Trace: > > [ 199.134333] drm_fbdev_cleanup+0x179/0x1a0 > > [ 199.134562] drm_fbdev_client_unregister+0x2b/0x40 > > [ 199.134828] drm_client_dev_unregister+0xa8/0x180 > > [ 199.135088] drm_dev_unregister+0x61/0x110 > > [ 199.135315] mgag200_pci_remove+0x38/0x52 [mgag200] > > [ 199.135586] pci_device_remove+0x62/0xe0 > > [ 199.135806] device_release_driver_internal+0x148/0x270 > > [ 199.136094] driver_detach+0x76/0xe0 > > [ 199.136294] bus_remove_driver+0x7e/0x100 > > [ 199.136521] pci_unregister_driver+0x28/0xf0 > > [ 199.136759] __x64_sys_delete_module+0x268/0x300 > > [ 199.137016] ? __ia32_sys_delete_module+0x300/0x300 > > [ 199.137285] ? call_rcu+0x3e4/0x580 > > [ 199.137481] ? fpregs_assert_state_consistent+0x4d/0x60 > > [ 199.137767] ? exit_to_user_mode_prepare+0x2f/0x130 > > [ 199.138037] do_syscall_64+0x33/0x40 > > [ 199.138237] entry_SYSCALL_64_after_hwframe+0x44/0xae > > [ 199.138517] RIP: 0033:0x7f36fdc3dcf7 > > > > Signed-off-by: Tong Zhang <ztong0001@xxxxxxxxx> > > --- > > drivers/gpu/drm/drm_fb_helper.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > > index b9a616737c0e..f6baa2046124 100644 > > --- a/drivers/gpu/drm/drm_fb_helper.c > > +++ b/drivers/gpu/drm/drm_fb_helper.c > > @@ -2048,7 +2048,7 @@ static void drm_fbdev_cleanup(struct drm_fb_helper *fb_helper) > > > > if (shadow) > > vfree(shadow); > > - else > > + else if (fb_helper->buffer) > > drm_client_buffer_vunmap(fb_helper->buffer); > > > > drm_client_framebuffer_delete(fb_helper->buffer); > > > > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Maxfeldstr. 5, 90409 Nürnberg, Germany > (HRB 36809, AG Nürnberg) > Geschäftsführer: Felix Imendörffer > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
