Hi, Sounds good to me.
Thanks, Yaroslav. -----Original Message----- From: Adrien Mazarguil [mailto:adrien.mazarg...@6wind.com] Sent: Wednesday, July 25, 2018 12:25 To: Yaroslav Brustinov (ybrustin) <ybrus...@cisco.com> Cc: Shahaf Shuler <shah...@mellanox.com>; Yongseok Koh <ys...@mellanox.com>; dev@dpdk.org; sta...@dpdk.org; Nélio Laranjeiro <nelio.laranje...@6wind.com>; Hanoch Haim (hhaim) <hh...@cisco.com> Subject: Re: [PATCH] net/mlx5: fix linkage error for glue lib On Wed, Jul 25, 2018 at 07:38:39AM +0000, Yaroslav Brustinov (ybrustin) wrote: > +Hanoch > > I've added -std=c11 flag to our compilation to check. > > Without alignas(max_align_t): > /usr/bin/ld: Warning: alignment 8 of symbol `mlx5_glue' in > src/dpdk/drivers/net/mlx5/mlx5_glue.c.11.o is smaller than 32 in > src/dpdk/drivers/net/mlx5/mlx5_rxq.c.11.o > > With alignas(max_align_t): > /usr/bin/ld: Warning: alignment 16 of symbol `mlx5_glue' in > src/dpdk/drivers/net/mlx5/mlx5_glue.c.11.o is smaller than 32 in > src/dpdk/drivers/net/mlx5/mlx5_rxq.c.11.o > > Using alignas(64) does not produce linker warning. OK, let's forget max_align_t. Even better, how about alignas(RTE_CACHE_LINE_SIZE) just in case the same GCC version complains about the lack of a 128 byte alignment on architectures like IBM POWER8. (remember to #include <rte_config.h> for RTE_CACHE_LINE_SIZE) > -----Original Message----- > From: Adrien Mazarguil [mailto:adrien.mazarg...@6wind.com] > Sent: Tuesday, July 24, 2018 19:04 > To: Yaroslav Brustinov (ybrustin) <ybrus...@cisco.com> > Cc: Shahaf Shuler <shah...@mellanox.com>; Yongseok Koh > <ys...@mellanox.com>; dev@dpdk.org; sta...@dpdk.org; Nélio Laranjeiro > <nelio.laranje...@6wind.com> > Subject: Re: [PATCH] net/mlx5: fix linkage error for glue lib > > On Tue, Jul 24, 2018 at 02:24:12PM +0000, Yaroslav Brustinov (ybrustin) wrote: > > Hi, > > > > Are you OK with C11? > > I saw in file dpdk/drivers/net/mlx4/mlx4_utils.c: > > > > * C11 code would include stdalign.h and use alignof(max_align_t) > > however > > * we'll stick with C99 for the time being. > > > > :) > > Hah, this code was originally intended to become a generic EAL function hence > the C99 but got rejected. Mellanox PMDs otherwise rely on C11 features > already. > > > As far as I understand, the issue is alignment of the pointer itself, not > > the struct. > > I'm not familiar with this command: "alignof(max_align_t)". > > Applying this on the struct: > > > > struct mlx5_glue { > > ... > > } __attribute__((__aligned__(64))); > > > > struct __attribute__((__aligned__(64))) mlx5_glue { > > ... > > }; > > > > ...still keeps the linker unhappy. > > Right, this was my first (wrong) suggestion that doesn't work on > types. How about the second one instead? Here's how the diff on > mlx5_glue.h should look > like: > > +#include <stdalign.h> > #include <stddef.h> > #include <stdint.h> > > [...] > > +alignas(max_align_t) > const struct mlx5_glue *mlx5_glue; > > Another comment regarding this patch, commit log should probably mention it > addresses a GCC bug that cannot be reproduced with latter versions. Keep in > mind DPDK recommends to use at least GCC version 4.9. > > > -----Original Message----- > > From: Shahaf Shuler [mailto:shah...@mellanox.com] > > Sent: Tuesday, July 24, 2018 16:51 > > To: Adrien Mazarguil <adrien.mazarg...@6wind.com> > > Cc: Yongseok Koh <ys...@mellanox.com>; dev@dpdk.org; Yaroslav > > Brustinov (ybrustin) <ybrus...@cisco.com>; sta...@dpdk.org; Nélio > > Laranjeiro <nelio.laranje...@6wind.com> > > Subject: RE: [PATCH] net/mlx5: fix linkage error for glue lib > > > > Yaroslav, > > > > Tuesday, July 24, 2018 3:06 PM, Adrien Mazarguil: > > > Subject: Re: [PATCH] net/mlx5: fix linkage error for glue lib > > > > Odd, how could this happen assuming both files are compiled > > > > during the same run using identical flags? Looks like a compiler issue. > > > > > > > > Anyway, may I suggest an alignment constraint on the structure > > > > type in mlx5_glue.h instead, so that all users inherit it. E.g. using > > > > C11 syntax: > > > > > > > > #include <stdalign.h> > > > > #include <stddef.h> > > > > > > > > [...] > > > > alignas(max_align_t) > > > > struct mlx5_glue { > > > > [...] > > > > }; > > > > > > My bad, this is not a correct use for alignas(), it doesn't work on types. > > > How about this instead: > > > > > > alignas(max_align_t) > > > const struct mlx5_glue *mlx5_glue; > > > > Can you confirm the above suggestion fixes your issue? > > > > > > > > > > > -- > Adrien Mazarguil > 6WIND -- Adrien Mazarguil 6WIND
