From ca8cb69580236f47041dd045c08f82cb7bb50d7c Mon Sep 17 00:00:00 2001
From: Lucas Stach <l.stach@pengutronix.de>
Date: Wed, 16 Oct 2019 15:37:06 +0200
Subject: drm/etnaviv: fix deadlock in GPU coredump
Git-commit: ca8cb69580236f47041dd045c08f82cb7bb50d7c
Patch-mainline: v5.4-rc6
References: bsc#1152472
The GPU coredump function violates the locking order by holding the MMU
context lock while trying to acquire the etnaviv_gem_object lock. This
results in a possible ABBA deadlock with other codepaths which follow
the established locking order.
Fortunately this is easy to fix by dropping the MMU context lock
earlier, as the BO dumping doesn't need the MMU context to be stable.
The only thing the BO dumping cares about are the BO mappings, which
are stable across the lifetime of the job.
Fixes: 27b67278e007 (drm/etnaviv: rework MMU handling)
[ Not really the first bad commit, but the one where this fix applies
cleanly. Stable kernels need a manual backport. ]
Reported-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/gpu/drm/etnaviv/etnaviv_dump.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_dump.c b/drivers/gpu/drm/etnaviv/etnaviv_dump.c
index 698db540972c..648cf0207309 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_dump.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_dump.c
@@ -180,6 +180,8 @@ void etnaviv_core_dump(struct etnaviv_gem_submit *submit)
etnaviv_cmdbuf_get_va(&submit->cmdbuf,
&gpu->mmu_context->cmdbuf_mapping));
+ mutex_unlock(&gpu->mmu_context->lock);
+
/* Reserve space for the bomap */
if (n_bomap_pages) {
bomap_start = bomap = iter.data;
@@ -221,8 +223,6 @@ void etnaviv_core_dump(struct etnaviv_gem_submit *submit)
obj->base.size);
}
- mutex_unlock(&gpu->mmu_context->lock);
-
etnaviv_core_dump_header(&iter, ETDUMP_BUF_END, iter.data);
dev_coredumpv(gpu->dev, iter.start, iter.data - iter.start, GFP_KERNEL);
--
2.28.0