| Message ID | 20171211114600.3636211-1-arnd@arndb.de |
|---|---|
| State | Accepted |
| Commit | 1b19b95169cd52fe82cd442fec0b279fe25cc838 |
| Headers | show |
| Series | IB/mlx5: revisit -Wmaybe-uninitialized warning | expand |
On Mon, Dec 11, 2017 at 12:45:44PM +0100, Arnd Bergmann wrote: > A warning that I thought I had fixed before occasionally comes > back in rare randconfig builds (I found 7 instances in the last > 100000 builds, originally it was much more frequent): > > drivers/infiniband/hw/mlx5/mr.c: In function 'mlx5_ib_reg_user_mr': > drivers/infiniband/hw/mlx5/mr.c:1229:5: error: 'order' may be used uninitialized in this function [-Werror=maybe-uninitialized] > if (order <= mr_cache_max_order(dev)) { > ^ > drivers/infiniband/hw/mlx5/mr.c:1247:8: error: 'ncont' may be used uninitialized in this function [-Werror=maybe-uninitialized] > drivers/infiniband/hw/mlx5/mr.c:1247:8: error: 'page_shift' may be used uninitialized in this function [-Werror=maybe-uninitialized] > drivers/infiniband/hw/mlx5/mr.c:1260:2: error: 'npages' may be used uninitialized in this function [-Werror=maybe-uninitialized] > > I've looked at all those findings again and noticed that they are all > with CONFIG_INFINIBAND_USER_MEM=n, which means ib_umem_get() returns > an error unconditionally and we never initialize or use those variables. > This triggers a condition in gcc iff mr_umem_get() is partially but not > entirely inlined, which in turn depends on the exact combination of > optimization settings. This is a known problem with gcc, with no > easy solution in the compiler, so this adds another workaround that > should be more reliable than my previous attempt. > > Returning an error from mlx5_ib_reg_user_mr() earlier means that we > can completely bypass the logic that caused the warning, the compiler > can now see that the variable is never accessed. > > Fixes: 14ab8896f5d9 ("IB/mlx5: avoid bogus -Wmaybe-uninitialized warning") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > drivers/infiniband/hw/mlx5/mr.c | 3 +++ > 1 file changed, 3 insertions(+) Appled to for-next, thanks Jason
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c index ee0ee1f9994b..ad37d8441fa2 100644 --- a/drivers/infiniband/hw/mlx5/mr.c +++ b/drivers/infiniband/hw/mlx5/mr.c @@ -1206,6 +1206,9 @@ struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, u64 start, u64 length, int err; bool use_umr = true; + if (!IS_ENABLED(CONFIG_INFINIBAND_USER_MEM)) + return ERR_PTR(-EINVAL); + mlx5_ib_dbg(dev, "start 0x%llx, virt_addr 0x%llx, length 0x%llx, access_flags 0x%x\n", start, virt_addr, length, access_flags);
A warning that I thought I had fixed before occasionally comes back in rare randconfig builds (I found 7 instances in the last 100000 builds, originally it was much more frequent): drivers/infiniband/hw/mlx5/mr.c: In function 'mlx5_ib_reg_user_mr': drivers/infiniband/hw/mlx5/mr.c:1229:5: error: 'order' may be used uninitialized in this function [-Werror=maybe-uninitialized] if (order <= mr_cache_max_order(dev)) { ^ drivers/infiniband/hw/mlx5/mr.c:1247:8: error: 'ncont' may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/infiniband/hw/mlx5/mr.c:1247:8: error: 'page_shift' may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/infiniband/hw/mlx5/mr.c:1260:2: error: 'npages' may be used uninitialized in this function [-Werror=maybe-uninitialized] I've looked at all those findings again and noticed that they are all with CONFIG_INFINIBAND_USER_MEM=n, which means ib_umem_get() returns an error unconditionally and we never initialize or use those variables. This triggers a condition in gcc iff mr_umem_get() is partially but not entirely inlined, which in turn depends on the exact combination of optimization settings. This is a known problem with gcc, with no easy solution in the compiler, so this adds another workaround that should be more reliable than my previous attempt. Returning an error from mlx5_ib_reg_user_mr() earlier means that we can completely bypass the logic that caused the warning, the compiler can now see that the variable is never accessed. Fixes: 14ab8896f5d9 ("IB/mlx5: avoid bogus -Wmaybe-uninitialized warning") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- drivers/infiniband/hw/mlx5/mr.c | 3 +++ 1 file changed, 3 insertions(+) -- 2.9.0