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From:   Nicholas Mc Guire <hofrat@osadl.org>
To:     Gustavo Padovan <gustavo@padovan.org>
Cc:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Sean Paul <seanpaul@chromium.org>,
        David Airlie <airlied@linux.ie>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Nicholas Mc Guire <hofrat@osadl.org>
Subject: [PATCH] drm: re-enable error handling
Date:   Sat, 14 Jul 2018 14:32:12 +0200
Message-Id: <1531571532-22733-1-git-send-email-hofrat@osadl.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

drm_legacy_ctxbitmap_next() returns idr_alloc() which can return
-ENOMEM, -EINVAL or -ENOSPC none of which are -1 . but the call sites 
of drm_legacy_ctxbitmap_next() seem to be assuming that the error case
would be -1 (original return of drm_ctxbitmap_next() prior to 2.6.23
was actually -1). Thus reenable error handling by checking for < 0.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Fixes: 62968144e673 ("drm: convert drm context code to use Linux idr")
---

Problem located with experimental coccinelle script

The noted Fixes tag is one of the commits that removed the -1 return
value in 2.6.23 in drm_ctxbitmap_next() but thats not the only change
that must have taken place to invalidate the error check.

Patch was compile tested with: x86_64_defconfig

Patch is against 4.18-rc4 (localversion-next is next-20180713)

 drivers/gpu/drm/drm_context.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_context.c b/drivers/gpu/drm/drm_context.c
index 3c4000f..f973d28 100644
--- a/drivers/gpu/drm/drm_context.c
+++ b/drivers/gpu/drm/drm_context.c
@@ -372,7 +372,7 @@ int drm_legacy_addctx(struct drm_device *dev, void *data,
 		ctx->handle = drm_legacy_ctxbitmap_next(dev);
 	}
 	DRM_DEBUG("%d\n", ctx->handle);
-	if (ctx->handle == -1) {
+	if (ctx->handle < 0) {
 		DRM_DEBUG("Not enough free contexts.\n");
 		/* Should this return -EBUSY instead? */
 		return -ENOMEM;
-- 
2.1.4