Hi, Here is an updated RFC round of the Restartable Sequences patchset based on kernel 4.17-rc3. Based on feedback from Linus, I'm introducing only the rseq system call, keeping the rest for later. This already enables speeding up the Facebook jemalloc and arm64 PMC read from user-space use-cases, as well as speedup of use-cases relying on getting the current cpu number from user-space. We'll have to wait until a more complete solution is introduced before the LTTng-UST tracer can replace its ring buffer atomic instructions with rseq though. But let's proceed one step at a time. The main change introduced by the removal of cpu_opv from this series in terms of library use from user-space is that APIs that previously took a CPU number as argument now only act on the current CPU. So for instance, this turns: int cpu = rseq_per_cpu_lock(lock, target_cpu); [...] rseq_per_cpu_unlock(lock, cpu); into int cpu = rseq_this_cpu_lock(lock); [...] rseq_per_cpu_unlock(lock, cpu); and: per_cpu_list_push(list, node, target_cpu); [...] per_cpu_list_pop(list, node, target_cpu); into this_cpu_list_push(list, node, &cpu); /* cpu is an output parameter. */ [...] node = this_cpu_list_pop(list, &cpu); /* cpu is an output parameter. */ Eventually integrating cpu_opv or some alternative will allow passing the cpu number as parameter rather than requiring the algorithm to work on the current CPU. The second effect of not having the cpu_opv fallback is that line and instruction single-stepping with a debugger transforms rseq critical sections based on retry loops into never-ending loops. Debuggers need to use the __rseq_table section to skip those critical sections in order to correctly behave when single-stepping a thread which uses rseq in a retry loop. However, applications which use an alternative fallback method rather than retrying on rseq fast-path abort won't be affected by this kind of single-stepping issue. Feedback is welcome! Thanks, Mathieu Boqun Feng (2): powerpc: Add support for restartable sequences powerpc: Wire up restartable sequences system call Mathieu Desnoyers (12): uapi headers: Provide types_32_64.h (v2) rseq: Introduce restartable sequences system call (v13) arm: Add restartable sequences support arm: Wire up restartable sequences system call x86: Add support for restartable sequences (v2) x86: Wire up restartable sequence system call selftests: lib.mk: Introduce OVERRIDE_TARGETS rseq: selftests: Provide rseq library (v5) rseq: selftests: Provide basic test rseq: selftests: Provide basic percpu ops test (v2) rseq: selftests: Provide parametrized tests (v2) rseq: selftests: Provide Makefile, scripts, gitignore (v2) MAINTAINERS | 12 + arch/Kconfig | 7 + arch/arm/Kconfig | 1 + arch/arm/kernel/signal.c | 7 + arch/arm/tools/syscall.tbl | 1 + arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/systbl.h | 1 + arch/powerpc/include/asm/unistd.h | 2 +- arch/powerpc/include/uapi/asm/unistd.h | 1 + arch/powerpc/kernel/signal.c | 3 + arch/x86/Kconfig | 1 + arch/x86/entry/common.c | 3 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/x86/kernel/signal.c | 6 + fs/exec.c | 1 + include/linux/sched.h | 134 +++ include/linux/syscalls.h | 4 +- include/trace/events/rseq.h | 56 + include/uapi/linux/rseq.h | 150 +++ include/uapi/linux/types_32_64.h | 67 ++ init/Kconfig | 23 + kernel/Makefile | 1 + kernel/fork.c | 2 + kernel/rseq.c | 366 ++++++ kernel/sched/core.c | 2 + kernel/sys_ni.c | 3 + tools/testing/selftests/Makefile | 1 + tools/testing/selftests/lib.mk | 4 + tools/testing/selftests/rseq/.gitignore | 6 + tools/testing/selftests/rseq/Makefile | 29 + .../testing/selftests/rseq/basic_percpu_ops_test.c | 312 +++++ tools/testing/selftests/rseq/basic_test.c | 55 + tools/testing/selftests/rseq/param_test.c | 1259 ++++++++++++++++++++ tools/testing/selftests/rseq/rseq-arm.h | 732 ++++++++++++ tools/testing/selftests/rseq/rseq-ppc.h | 688 +++++++++++ tools/testing/selftests/rseq/rseq-skip.h | 82 ++ tools/testing/selftests/rseq/rseq-x86.h | 1149 ++++++++++++++++++ tools/testing/selftests/rseq/rseq.c | 116 ++ tools/testing/selftests/rseq/rseq.h | 164 +++ tools/testing/selftests/rseq/run_param_test.sh | 120 ++ 41 files changed, 5572 insertions(+), 2 deletions(-) create mode 100644 include/trace/events/rseq.h create mode 100644 include/uapi/linux/rseq.h create mode 100644 include/uapi/linux/types_32_64.h create mode 100644 kernel/rseq.c create mode 100644 tools/testing/selftests/rseq/.gitignore create mode 100644 tools/testing/selftests/rseq/Makefile create mode 100644 tools/testing/selftests/rseq/basic_percpu_ops_test.c create mode 100644 tools/testing/selftests/rseq/basic_test.c create mode 100644 tools/testing/selftests/rseq/param_test.c create mode 100644 tools/testing/selftests/rseq/rseq-arm.h create mode 100644 tools/testing/selftests/rseq/rseq-ppc.h create mode 100644 tools/testing/selftests/rseq/rseq-skip.h create mode 100644 tools/testing/selftests/rseq/rseq-x86.h create mode 100644 tools/testing/selftests/rseq/rseq.c create mode 100644 tools/testing/selftests/rseq/rseq.h create mode 100755 tools/testing/selftests/rseq/run_param_test.sh -- 2.11.0 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
