drm/i915: Break up error capture compression loops with cond_resched()

As the error capture will compress user buffers as directed to by the
user, it can take an arbitrary amount of time and space. Break up the
compression loops with a call to cond_resched(), that will allow other
processes to schedule (avoiding the soft lockups) and also serve as a
warning should we try to make this loop atomic in the future.

Testcase: igt/gem_exec_capture/many-*
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200916090059.3189-2-chris@chris-wilson.co.uk
(cherry picked from commit 293f43c80c0027ff9299036c24218ac705ce584e)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -311,6 +311,8 @@ static int compress_page(struct i915_vma_compress *c,
 
 		if (zlib_deflate(zstream, Z_NO_FLUSH) != Z_OK)
 			return -EIO;
+
+		cond_resched();
 	} while (zstream->avail_in);
 
 	/* Fallback to uncompressed if we increase size? */
@@ -397,6 +399,7 @@ static int compress_page(struct i915_vma_compress *c,
 	if (!(wc && i915_memcpy_from_wc(ptr, src, PAGE_SIZE)))
 		memcpy(ptr, src, PAGE_SIZE);
 	dst->pages[dst->page_count++] = ptr;
+	cond_resched();
 
 	return 0;
 }