On Tue, 26 Sept 2023 at 21:51, Florian Weimer <fweimer@xxxxxxxxxx> wrote: > > * Dmitry Vyukov: > > > In reality it's a bit more involved since the field is actually 8 > > bytes and only partially overlaps with rseq.cpu_id_start (it's an > > 8-byte pointer with high 4 bytes overlap rseq.cpu_id_start): > > > > https://github.com/google/tcmalloc/blob/229908285e216cca8b844c1781bf16b838128d1b/tcmalloc/internal/percpu.h#L101-L165 > > This does not compose with other rseq users, as noted in the sources: > > // Note: this makes __rseq_abi.cpu_id_start unusable for its original purpose. > > For a core library such a malloc replacement, that is a very bad trap. I agree. I wouldn't do this if there were other options. That's why I am looking for official kernel support for this. If we would have a separate 8 bytes that are overwritten with 0 when a thread is descheduled, that would be perfect.
