Dear Chuansheng,
Am 31.03.22 um 02:06 schrieb Liu, Chuansheng:
-----Original Message----- From: Paul Menzel pmenzel@molgen.mpg.de Sent: Thursday, March 31, 2022 12:47 AM
[…]
Am 29.03.22 um 01:58 schrieb Liu, Chuansheng:
-----Original Message----- From: Paul Menzel Sent: Monday, March 28, 2022 2:15 PM
Am 28.03.22 um 02:58 schrieb Liu, Chuansheng:
-----Original Message-----
Sent: Saturday, March 26, 2022 4:11 PM
Am 17.03.22 um 06:46 schrieb Chuansheng Liu: > Easily hit the below list corruption: > == > list_add corruption. prev->next should be next (ffffffffc0ceb090), but > was ffffec604507edc8. (prev=ffffec604507edc8). > WARNING: CPU: 65 PID: 3959 at lib/list_debug.c:26 > __list_add_valid+0x53/0x80 > CPU: 65 PID: 3959 Comm: fbdev Tainted: G U > RIP: 0010:__list_add_valid+0x53/0x80 > Call Trace: > <TASK> > fb_deferred_io_mkwrite+0xea/0x150 > do_page_mkwrite+0x57/0xc0 > do_wp_page+0x278/0x2f0 > __handle_mm_fault+0xdc2/0x1590 > handle_mm_fault+0xdd/0x2c0 > do_user_addr_fault+0x1d3/0x650 > exc_page_fault+0x77/0x180 > ? asm_exc_page_fault+0x8/0x30 > asm_exc_page_fault+0x1e/0x30 > RIP: 0033:0x7fd98fc8fad1 > == > > Figure out the race happens when one process is adding &page->lru into > the pagelist tail in fb_deferred_io_mkwrite(), another process is > re-initializing the same &page->lru in fb_deferred_io_fault(), which is > not protected by the lock. > > This fix is to init all the page lists one time during initialization, > it not only fixes the list corruption, but also avoids INIT_LIST_HEAD() > redundantly. > > Fixes: 105a940416fc ("fbdev/defio: Early-out if page is already enlisted") > Cc: Thomas Zimmermann tzimmermann@suse.de > Signed-off-by: Chuansheng Liu chuansheng.liu@intel.com > --- > drivers/video/fbdev/core/fb_defio.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c > index 98b0f23bf5e2..eafb66ca4f28 100644 > --- a/drivers/video/fbdev/core/fb_defio.c > +++ b/drivers/video/fbdev/core/fb_defio.c > @@ -59,7 +59,6 @@ static vm_fault_t fb_deferred_io_fault(struct vm_fault *vmf) > printk(KERN_ERR "no mapping available\n"); > > BUG_ON(!page->mapping); > - INIT_LIST_HEAD(&page->lru); > page->index = vmf->pgoff; > > vmf->page = page; > @@ -220,6 +219,8 @@ static void fb_deferred_io_work(struct work_struct *work) > void fb_deferred_io_init(struct fb_info *info) > { > struct fb_deferred_io *fbdefio = info->fbdefio; > + struct page *page; > + int i; > > BUG_ON(!fbdefio); > mutex_init(&fbdefio->lock); > @@ -227,6 +228,12 @@ void fb_deferred_io_init(struct fb_info *info) > INIT_LIST_HEAD(&fbdefio->pagelist); > if (fbdefio->delay == 0) /* set a default of 1 s */ > fbdefio->delay = HZ; > + > + /* initialize all the page lists one time */ > + for (i = 0; i < info->fix.smem_len; i += PAGE_SIZE) { > + page = fb_deferred_io_page(info, i); > + INIT_LIST_HEAD(&page->lru); > + } > } > EXPORT_SYMBOL_GPL(fb_deferred_io_init); > Applying your patch on top of current Linus’ master branch, tty0 is unusable and looks frozen. Sometimes network card still works, sometimes not.
I don't see how the patch would cause below BUG call stack, need some time to debug. Just few comments:
- Will the system work well without this patch?
Yes, the framebuffer works well without the patch.
- When you are sure the patch causes the regression you saw, please get free
to submit one reverted patch, thanks : )
I think you for patch wasn’t submitted yet – at least not pulled by Linus.
The patch has been in drm-tip, could you have a try with the latest drm-tip to see if the Framebuffer works well, in that case, we could revert it in drm-tip then.
With drm-tip (drm-tip: 2022y-03m-29d-13h-14m-35s UTC integration manifest) everything works fine. (I had to disable amdgpu driver, as it failed to build.) Is anyone able to explain that?
My patch is for fixing another patch which is in the drm-tip at least,
The referenced commit 105a940416fc in the Fixes tag is also in Linus’ master branch.
so I assume applying my patch into Linus tree directly is not completely proper. That's my intention of asking your help for retesting drm-tip.
If there were such a relation, that would need to be documented in the commit message.
You mean everything working fine means another issue you hit is also gone?
No, I just mean the hang when applying your patch.
Anyway, after figuring out, that drm-tip, is actually not behind Linus’ master branch, I tried to figure out the differences, and it turns out it’s also related to commit fac54e2bfb5b (x86/Kconfig: Select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP) [1], which is in Linus’ master branch, but not drm-tip. Note, I am using a 32-bit user space and a 64-bit Linux kernel. Reverting commit fac54e2bfb5b, and having your patch a applied, the hang is gone.
I am adding the people involved in the other discussion to make them aware of this failure case.
Kind regards,
Paul
[1]: https://linux-regtracking.leemhuis.info/regzbot/mainline/