drm/imagination: avoid deadlock on fence release

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/imagination: avoid deadlock on fence release Do scheduler queue fence release processing on a workqueue, rather than in the release function itself. Fixes deadlock issues such as the following: [ 607.400437] ============================================ [ 607.405755] WARNING: possible recursive locking detected [ 607.415500] -------------------------------------------- [ 607.420817] weston:zfq0/24149 is trying to acquire lock: [ 607.426131] ffff000017d041a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: pvr_gem_object_vunmap+0x40/0xc0 [powervr] [ 607.436728] but task is already holding lock: [ 607.442554] ffff000017d105a0 (reservation_ww_class_mutex){+.+.}-{3:3}, at: dma_buf_ioctl+0x250/0x554 [ 607.451727] other info that might help us debug this: [ 607.458245] Possible unsafe locking scenario: [ 607.464155] CPU0 [ 607.466601] ---- [ 607.469044] lock(reservation_ww_class_mutex); [ 607.473584] lock(reservation_ww_class_mutex); [ 607.478114] *** DEADLOCK ***

References

• https://git.kernel.org/stable/c/d993ae7360923efd6ade43a32043459a121c28c1
• https://git.kernel.org/stable/c/9bd8b8d34cf4efba18766d64f817c819ed1bbde7
• https://git.kernel.org/stable/c/df1a1ed5e1bdd9cc13148e0e5549f5ebcf76cf13