We try hard to select a suitable hole in the drm_mm first time. But if that is unsuccessful, we then have to look at neighbouring nodes, and this requires traversing the rbtree. Walking the rbtree can be slow (much slower than a linear list for deep trees), and if the drm_mm has been purposefully fragmented our search can be trapped for a long, long time. For non-preemptible kernels, we need to break up long CPU bound sections by manually checking for cond_resched(); similarly we should also bail out if we have been told to terminate. (In an ideal world, we would break for any signal, but we need to trade off having to perform the search again after ERESTARTSYS, which again may form a trap of making no forward progress.)
Reported-by: Zbigniew Kempczyński <zbigniew.kempczyn...@intel.com> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> Cc: Zbigniew Kempczyński <zbigniew.kempczyn...@intel.com> Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com> --- drivers/gpu/drm/drm_mm.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c index 2a6e34663146..47d5de9ca0a8 100644 --- a/drivers/gpu/drm/drm_mm.c +++ b/drivers/gpu/drm/drm_mm.c @@ -45,6 +45,7 @@ #include <linux/export.h> #include <linux/interval_tree_generic.h> #include <linux/seq_file.h> +#include <linux/sched/signal.h> #include <linux/slab.h> #include <linux/stacktrace.h> @@ -366,6 +367,11 @@ next_hole(struct drm_mm *mm, struct drm_mm_node *node, enum drm_mm_insert_mode mode) { + /* Searching is slow; check if we ran out of time/patience */ + cond_resched(); + if (fatal_signal_pending(current)) + return NULL; + switch (mode) { default: case DRM_MM_INSERT_BEST: @@ -557,7 +563,7 @@ int drm_mm_insert_node_in_range(struct drm_mm * const mm, return 0; } - return -ENOSPC; + return signal_pending(current) ? -ERESTARTSYS : -ENOSPC; } EXPORT_SYMBOL(drm_mm_insert_node_in_range); -- 2.25.0 _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel