On Sat, 2014-01-11 at 21:55 -0600, Larry Finger wrote: > On 01/11/2014 09:27 PM, Ben Hutchings wrote: > > On Sat, 2014-01-11 at 13:48 -0600, Larry Finger wrote: > >> On openSUSE systems, the script that installs the firmware for b43 also > >> unloads and reloads the driver. When the firmware was not previously > >> available, the driver has stalled at a wait_for_completion(). When the > >> unload routine releases that hold, the driver encounters structures > >> that have already been deleted and generates a fatal condition. When > >> the user does a manual restart, the file system cleanup frequently > >> results in the firmware files being deleted and the user is never able > >> to install the firmware. The fix is to change the wait_for_completion() > >> with a wait_for_completion_timeout() with a 60 second wait period. > >> > >> There is a potential race condition; however, the chances that less > >> than a minute has elapsed between the initial driver load and a > >> subsequent unload is very unlikely. > > > > A minute-long race is 'unlikely' to be hit? Seriously?! > > Ben, > > If you force a reboot before the minute expires, nothing weird happens. The only > race condition happens when the user has to ...remove the module. Exactly how the bug reporter triggered module removal seems irrelevant. > log in, open a terminal, run a > script that downloads 13.5 MiB of files from the Internet, and then executes the > firmware extraction program. On my 10 Mbps external line and a 2 GHz CPU, that > takes 32 s, plus any time to enter the password for a sudo operation. That was > the basis for my conclusion that a race is unlikely. > > What is the minimum time that should be allowed for a request_firmware_nowait() > to respond? I know we had to go to asynchronous fw loading because the > synchronous version would timeout at 30 s. You could switch back to synchronous firmware loading soon, as it's not going to support a usermode helper any more. But until then, the proper fix for this is going to be to cancel the waiter earlier in teardown. Ben. -- Ben Hutchings Quantity is no substitute for quality, but it's the only one we've got.
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