| From foo@baz Fri Mar 16 15:43:17 CET 2018 |
| From: Arnd Bergmann <arnd@arndb.de> |
| Date: Mon, 11 Dec 2017 12:45:44 +0100 |
| Subject: IB/mlx5: revisit -Wmaybe-uninitialized warning |
| |
| From: Arnd Bergmann <arnd@arndb.de> |
| |
| |
| [ Upstream commit 1b19b95169cd52fe82cd442fec0b279fe25cc838 ] |
| |
| 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> |
| Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/infiniband/hw/mlx5/mr.c | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| --- 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 |
| 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); |
| |
