Hi Paul,
-----Original Message----- From: Paul Menzel pmenzel@molgen.mpg.de Sent: Thursday, March 31, 2022 12:47 AM To: Liu, Chuansheng chuansheng.liu@intel.com Cc: tzimmermann@suse.de; linux-fbdev@vger.kernel.org; deller@gmx.de; dri- devel@lists.freedesktop.org Subject: Re: [PATCH] fbdev: defio: fix the pagelist corruption
[Cc: -jayalk@intworks.biz as it bounces]
Dear Chuansheng,
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, 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.
You mean everything working fine means another issue you hit is also gone?
Best Regards Chuansheng