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Re: Restartable Sequences system call merged into Linux

On 07/12/2018 10:10 AM, Szabolcs Nagy wrote:
On 11/07/18 17:03, Stefan Liebler wrote:
On 06/11/2018 09:49 PM, Mathieu Desnoyers wrote:

Good news! The restartable sequences (rseq) system call is now merged into the master
branch of the Linux kernel within the 4.18 merge window:

It would be important to discuss how we should proceed to integrate the library part of rseq (see tools/testing/selftests/rseq/rseq*.{ch}) into glibc, or if it should
live in a standalone project.

It should be noted that there can be only one rseq TLS area registered per thread, which can then be used by many libraries and by the executable, so this is a
process-wide (per-thread) resource that we need to manage carefully.

Thoughts ?



The structs rseq_cs and rseq are aligned to 32 bytes.
Please have a look at the bug:
"Bug 23403 - Wrong alignment of TLS variables"

@Carlos or somebody else:
Should this be fixed in the upcoming glibc release?

i think s390 can implement a hack that increases the internal
pthread_t alignment to 64 or similar.

that effectively fixes 2.28 in practice (huge tls alignment
should be rare).

Yes, this hack would fix it, but on the other side it hides a real bug.
Therefore I prefer Florian's idea that once it is fixed, it should be backported.

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