----- On Nov 22, 2017, at 2:38 PM, Peter Zijlstra peterz@infradead.org wrote:

On Tue, Nov 21, 2017 at 09:18:53AM -0500, Mathieu Desnoyers wrote:

...

Implements two basic tests of RSEQ functionality, and one more exhaustive parameterizable test.

The first, "basic_test" only asserts that RSEQ works moderately correctly. E.g. that the CPUID pointer works.

"basic_percpu_ops_test" is a slightly more "realistic" variant, implementing a few simple per-cpu operations and testing their correctness.

"param_test" is a parametrizable restartable sequences test. See the "--help" output for usage.

A run_param_test.sh script runs many variants of the parametrizable tests.

As part of those tests, a helper library "rseq" implements a user-space API around restartable sequences. It uses the cpu_opv system call as fallback when single-stepped by a debugger. It exposes the instruction pointer addresses where the rseq assembly blocks begin and end, as well as the associated abort instruction pointer, in the __rseq_table section. This section allows debuggers may know where to place breakpoints when single-stepping through assembly blocks which may be aborted at any point by the kernel.

Could I ask you to split this in smaller bits?

I'd start with just the rseq library, using only the rseq interface. Then add the whole cpu_opv fallback stuff. Then add the selftests using librseq.

As is this is a tad much to read in a single go.

Sure, will do! And I plan to change the selftests to use the new "percpu_*()" API that removes the need to duplicate code in the caller code.

Thanks,

Mathieu