[STR]

• [1] Start Firefox
• [2] move to bugzilla bug like bug 1724949
• [3] Call "dxcap -forcetdr" from a console

[Actual Result]
Firefox window became blank

WebRender(Software) did not caused the problem. The problem does not always happen with the STR.

It seems like a regression. I did not saw the problem with STR in the past.

I tried the following mozregression.

• ./mach mozregression --good 2021-05-01 --bad 2021-05-15 --pref gfx.webrender.all:true -a https://bugzilla.mozilla.org/show_bug.cgi?id=1724949

It showed the following.

https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=ae1bf693f51a3345c68a8d4f4aaf76e4883f458c&tochange=ed8ff73df9a2bc82aa1a59a4d8106043c5b335c3

bug 1712665 is going to fix such a HW WR bug for Linux: https://phabricator.services.mozilla.com/D123792

Bug 1708325 added nsRefreshDriver::mPendingTransactions. It is not cleared during WebRenderLayerManager::DoDestroy(). Then nsRefreshDriver had 2 pending transact, then nsRefreshDriver did not trigger next rendering with new WebRenderLayerManager.

https://hg.mozilla.org/mozilla-central/rev/5f5504699d3c

Reproduced with Fx 93.0a1 (2021-08-26) on Windows 10, but only intermittently.
Verified fixed (checked several times since the reproducibility rate was not 100%) with Fx 94.0a1 (2021-09-13) and Fx 93.0b4 on Windows 10.

Is this something we should consider taking on ESR91? It grafts cleanly.

Comment on attachment 9238616 [details]
Bug 1727703 - Clear pending transactions in WebRenderLayerManager::DoDestroy()

ESR Uplift Approval Request

• If this is not a sec:{high,crit} bug, please state case for ESR consideration: When blank window happens, user could not use browser.
• User impact if declined: WebRender could cause blank window when device reset happens on Windows.
• Fix Landed on Version: 93.0b4
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): The change is a small fix during destroying WebRenderLayerManager. It affects to a case that WebRenderLayerManager is re-created. On Windows, it happens only when device reset or gpu process crash happen.
• String or UUID changes made by this patch: none

Comment on attachment 9238616 [details]
Bug 1727703 - Clear pending transactions in WebRenderLayerManager::DoDestroy()

Approved for 91.2esr.

https://hg.mozilla.org/releases/mozilla-esr91/rev/f315d49650c0