diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.14/950-0175-drm-vc4-Fix-false-positive-WARN-backtrace-on-refcoun.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.14/950-0175-drm-vc4-Fix-false-positive-WARN-backtrace-on-refcoun.patch | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/target/linux/brcm2708/patches-4.14/950-0175-drm-vc4-Fix-false-positive-WARN-backtrace-on-refcoun.patch b/target/linux/brcm2708/patches-4.14/950-0175-drm-vc4-Fix-false-positive-WARN-backtrace-on-refcoun.patch new file mode 100644 index 0000000000..0d3b4520d3 --- /dev/null +++ b/target/linux/brcm2708/patches-4.14/950-0175-drm-vc4-Fix-false-positive-WARN-backtrace-on-refcoun.patch @@ -0,0 +1,41 @@ +From 5537bac0e5c8f3634c5595c21c7d63f0c0263e0e Mon Sep 17 00:00:00 2001 +From: Boris Brezillon <boris.brezillon@free-electrons.com> +Date: Wed, 22 Nov 2017 21:39:28 +0100 +Subject: [PATCH 175/454] drm/vc4: Fix false positive WARN() backtrace on + refcount_inc() usage + +With CONFIG_REFCOUNT_FULL enabled, refcount_inc() complains when it's +passed a refcount object that has its counter set to 0. In this driver, +this is a valid use case since we want to increment ->usecnt only when +the BO object starts to be used by real HW components and this is +definitely not the case when the BO is created. + +Fix the problem by using refcount_inc_not_zero() instead of +refcount_inc() and fallback to refcount_set(1) when +refcount_inc_not_zero() returns false. Note that this 2-steps operation +is not racy here because the whole section is protected by a mutex +which guarantees that the counter does not change between the +refcount_inc_not_zero() and refcount_set() calls. + +Fixes: b9f19259b84d ("drm/vc4: Add the DRM_IOCTL_VC4_GEM_MADVISE ioctl") +Reported-by: Stefan Wahren <stefan.wahren@i2se.com> +Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> +Acked-by: Eric Anholt <eric@anholt.net> +Link: https://patchwork.freedesktop.org/patch/msgid/20171122203928.28135-1-boris.brezillon@free-electrons.com +(cherry picked from commit 5bfd40139d55790cbc8e56ad1ce4f974f1fa186d) +--- + drivers/gpu/drm/vc4/vc4_bo.c | 3 ++- + 1 file changed, 2 insertions(+), 1 deletion(-) + +--- a/drivers/gpu/drm/vc4/vc4_bo.c ++++ b/drivers/gpu/drm/vc4/vc4_bo.c +@@ -639,7 +639,8 @@ int vc4_bo_inc_usecnt(struct vc4_bo *bo) + mutex_lock(&bo->madv_lock); + switch (bo->madv) { + case VC4_MADV_WILLNEED: +- refcount_inc(&bo->usecnt); ++ if (!refcount_inc_not_zero(&bo->usecnt)) ++ refcount_set(&bo->usecnt, 1); + ret = 0; + break; + case VC4_MADV_DONTNEED: |