kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-11-13 07:31:07 +00:00
Code Issues Releases Packages Activity
linux/drivers/infiniband
History
Arnd Bergmann 4f33fcc68a IB/mlx5: revisit -Wmaybe-uninitialized warning 
[ Upstream commit 1b19b95169 ]

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: 14ab8896f5 ("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>
History 2018-03-19 08:42:56 +01:00
..
core IB/core: Fix missing RDMA cgroups release in case of failure to register device 2018-03-15 10:54:33 +01:00
hw IB/mlx5: revisit -Wmaybe-uninitialized warning 2018-03-19 08:42:56 +01:00
sw RDMA/rxe: Fix rxe_qp_cleanup() 2018-02-22 15:42:15 +01:00
ulp IB/ipoib: Fix race condition in neigh creation 2018-03-03 10:24:33 +01:00
Kconfig IB/core: Expose ioctl interface through experimental Kconfig 2017-08-31 08:35:14 -04:00
Makefile IB/rdmavt: Create module framework and handle driver registration 2016-03-10 20:37:04 -05:00