On 12/19/18 12:36 PM, Joseph Myers wrote: > On Wed, 19 Dec 2018, Vineet Gupta wrote: > >> So perhaps we keep the ARC header above, with matching layout, while >> switching to generic sigaction() still. OK ? > > If the different userspace layout is better, it should be better for all > future ports as well. > > Duplicating all the SA_* constants in architecture-specific headers, even > when those architectures don't actually have different values of those > constants, is bad, especially since there is logic about which __USE_* > macros get which SA_* defined which then needs to be duplicated. Totally agree. > So what this suggests to me is a preliminary patch series to unify > bits/sigaction.h headers - there might be one header for SA_* constants > (architecture-specific variants only when needed), one for SIG_* constants > (architecture-specific variants only when needed), and one for the ways in > which the layout of the userspace struct sigaction can vary (defining > macros that the unified bits/sigaction.h then uses to control the layout - > cf. the siginfo unification a while back). Actually this can be simplified. Given the asm-generic syscall ABI, we are anyhow locked into SA_* or SIG_* and kernel side sigaction, the only variant is user facing struct sigaction. I suppose we could leave it at that given that only 1 syscall sigaction is affected. The bigger bang for the buck will the reduction of sizeof(sigset_t) - purely from amount of memory any sig* call needs to read/write/copy. I'll follow Adhemerval's suggestion of arch-specific __sigset_t.h which seems doable w/o much pain. > Initially, the default version of that last header would correspond to the > existing sysdeps/unix/sysv/linux/bits/sigaction.h header - however, if you > get consensus for a different layout as the default for new architectures, > the default would change and all existing architectures that use the > current default layout would get copies of the new bits/ header configured > to keep the old layout. (Variants are possible to reduce the number of > architectures needing architecture-specific copies as a result of the > changed default. For example, you could have the new default only in > sysdeps/unix/sysv/linux/generic not sysdeps/unix/sysv/linux/ and then only > existing asm-generic architectures (aarch64 nios2 riscv) would need to > override back to the old default layout.) Yes this will require a needless churn all over, just for 1 syscall. _______________________________________________ linux-snps-arc mailing list linux-snps-arc@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-snps-arc
