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Date: Sat, 2 Jun 2018 08:43:52 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Peter Zijlstra <peterz@...radead.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
Boqun Feng <boqun.feng@...il.com>,
Andy Lutomirski <luto@...capital.net>,
Dave Watson <davejwatson@...com>
Cc: linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
Paul Turner <pjt@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Russell King <linux@....linux.org.uk>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H . Peter Anvin" <hpa@...or.com>, Andrew Hunter <ahh@...gle.com>,
Andi Kleen <andi@...stfloor.org>, Chris Lameter <cl@...ux.com>,
Ben Maurer <bmaurer@...com>,
Steven Rostedt <rostedt@...dmis.org>,
Josh Triplett <josh@...htriplett.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Michael Kerrisk <mtk.manpages@...il.com>,
Joel Fernandes <joelaf@...gle.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH for 4.18 00/16] Restartable Sequences
Hi,
Here is an updated RFC of the rseq patchset. It only includes rseq.
Further improvements are kept for later.
Compared to the previous version of this series, CONFIG_DEBUG_RSEQ=y now
ensures that system calls are not issued within a rseq critical section,
else the process is killed. This check, performed by rseq_syscall(), has
been wired up and tested on x86 32/64, arm 32, and powerpc 64. It has
only been wired up on powerpc 32 (still needs to be tested).
This 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
compared to the prior versions of 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.
Thanks for your feedback!
Mathieu
Boqun Feng (3):
powerpc: Add support for restartable sequences
powerpc: Add syscall detection for restartable sequences
powerpc: Wire up restartable sequences system call
Mathieu Desnoyers (13):
uapi headers: Provide types_32_64.h (v2)
rseq: Introduce restartable sequences system call (v13)
arm: Add restartable sequences support
arm: Add syscall detection for restartable sequences
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/entry-common.S | 25 +-
arch/arm/kernel/signal.c | 14 +
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/entry_32.S | 7 +
arch/powerpc/kernel/entry_64.S | 8 +
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 | 57 +
include/uapi/linux/rseq.h | 133 +++
include/uapi/linux/types_32_64.h | 50 +
init/Kconfig | 23 +
kernel/Makefile | 1 +
kernel/fork.c | 2 +
kernel/rseq.c | 357 ++++++
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 | 30 +
.../testing/selftests/rseq/basic_percpu_ops_test.c | 313 +++++
tools/testing/selftests/rseq/basic_test.c | 56 +
tools/testing/selftests/rseq/param_test.c | 1260 ++++++++++++++++++++
tools/testing/selftests/rseq/rseq-arm.h | 715 +++++++++++
tools/testing/selftests/rseq/rseq-ppc.h | 671 +++++++++++
tools/testing/selftests/rseq/rseq-skip.h | 65 +
tools/testing/selftests/rseq/rseq-x86.h | 1132 ++++++++++++++++++
tools/testing/selftests/rseq/rseq.c | 117 ++
tools/testing/selftests/rseq/rseq.h | 147 +++
tools/testing/selftests/rseq/run_param_test.sh | 121 ++
44 files changed, 5492 insertions(+), 8 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
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