lkml.org 
[lkml]   [2017]   [Dec]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: IB/mlx5: revisit -Wmaybe-uninitialized warning
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

\
 
 \ /
  Last update: 2017-12-12 00:41    [W:0.031 / U:0.096 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site