mirror of https://github.com/golang/go.git
4 Commits
| Author | SHA1 | Message | Date |
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Cherry Mui
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c426c87012 |
runtime/cgo: store M for C-created thread in pthread key
This reapplies CL 485500, with a fix drafted in CL 492987 incorporated. CL 485500 is reverted due to #60004 and #60007. #60004 is fixed in CL 492743. #60007 is fixed in CL 492987 (incorporated in this CL). [Original CL 485500 description] This reapplies CL 481061, with the followup fixes in CL 482975, CL 485315, and CL 485316 incorporated. CL 481061, by doujiang24 <doujiang24@gmail.com>, speed up C to Go calls by binding the M to the C thread. See below for its description. CL 482975 is a followup fix to a C declaration in testprogcgo. CL 485315 is a followup fix for x_cgo_getstackbound on Illumos. CL 485316 is a followup cleanup for ppc64 assembly. CL 479915 passed the G to _cgo_getstackbound for direct updates to gp.stack.lo. A G can be reused on a new thread after the previous thread exited. This could trigger the C TSAN race detector because it couldn't see the synchronization in Go (lockextra) preventing the same G from being used on multiple threads at the same time. We work around this by passing the address of a stack variable to _cgo_getstackbound rather than the G. The stack is generally unique per thread, so TSAN won't see the same address from multiple threads. Even if stacks are reused across threads by pthread, C TSAN should see the synchonization in the stack allocator. A regression test is added to misc/cgo/testsanitizer. [Original CL 481061 description] This reapplies CL 392854, with the followup fixes in CL 479255, CL 479915, and CL 481057 incorporated. CL 392854, by doujiang24 <doujiang24@gmail.com>, speed up C to Go calls by binding the M to the C thread. See below for its description. CL 479255 is a followup fix for a small bug in ARM assembly code. CL 479915 is another followup fix to address C to Go calls after the C code uses some stack, but that CL is also buggy. CL 481057, by Michael Knyszek, is a followup fix for a memory leak bug of CL 479915. [Original CL 392854 description] In a C thread, it's necessary to acquire an extra M by using needm while invoking a Go function from C. But, needm and dropm are heavy costs due to the signal-related syscalls. So, we change to not dropm while returning back to C, which means binding the extra M to the C thread until it exits, to avoid needm and dropm on each C to Go call. Instead, we only dropm while the C thread exits, so the extra M won't leak. When invoking a Go function from C: Allocate a pthread variable using pthread_key_create, only once per shared object, and register a thread-exit-time destructor. And store the g0 of the current m into the thread-specified value of the pthread key, only once per C thread, so that the destructor will put the extra M back onto the extra M list while the C thread exits. When returning back to C: Skip dropm in cgocallback, when the pthread variable has been created, so that the extra M will be reused the next time invoke a Go function from C. This is purely a performance optimization. The old version, in which needm & dropm happen on each cgo call, is still correct too, and we have to keep the old version on systems with cgo but without pthreads, like Windows. This optimization is significant, and the specific value depends on the OS system and CPU, but in general, it can be considered as 10x faster, for a simple Go function call from a C thread. For the newly added BenchmarkCGoInCThread, some benchmark results: 1. it's 28x faster, from 3395 ns/op to 121 ns/op, in darwin OS & Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz 2. it's 6.5x faster, from 1495 ns/op to 230 ns/op, in Linux OS & Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz [CL 479915 description] Currently, when C calls into Go the first time, we grab an M using needm, which sets m.g0's stack bounds using the SP. We don't know how big the stack is, so we simply assume 32K. Previously, when the Go function returns to C, we drop the M, and the next time C calls into Go, we put a new stack bound on the g0 based on the current SP. After CL 392854, we don't drop the M, and the next time C calls into Go, we reuse the same g0, without recomputing the stack bounds. If the C code uses quite a bit of stack space before calling into Go, the SP may be well below the 32K stack bound we assumed, so the runtime thinks the g0 stack overflows. This CL makes needm get a more accurate stack bound from pthread. (In some platforms this may still be a guess as we don't know exactly where we are in the C stack), but it is probably better than simply assuming 32K. [CL 492987 description] On the first call into Go from a C thread, currently we set the g0 stack's high bound imprecisely based on the SP. With CL 485500, we keep the M and don't recompute the stack bounds when it calls into Go again. If the first call is made when the C thread uses some deep stack, but a subsequent call is made with a shallower stack, the SP may be above g0.stack.hi. This is usually okay as we don't check usually stack.hi. One place where we do check for stack.hi is in the signal handler, in adjustSignalStack. In particular, C TSAN delivers signals on the g0 stack (instead of the usual signal stack). If the SP is above g0.stack.hi, we don't see it is on the g0 stack, and throws. This CL makes it get an accurate stack upper bound with the pthread API (on the platforms where it is available). Also add some debug print for the "handler not on signal stack" throw. Fixes #51676. Fixes #59294. Fixes #59678. Fixes #60007. Change-Id: Ie51c8e81ade34ec81d69fd7bce1fe0039a470776 Reviewed-on: https://go-review.googlesource.com/c/go/+/495855 Run-TryBot: Cherry Mui <cherryyz@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Michael Pratt <mpratt@google.com> |
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Austin Clements
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804850d87b |
cmd/cgo/internal/testcarchive: build on all platforms
This test package uses syscall.SIGSEGV and syscall.SIGPIPE, which are defined on most, but not all platforms. Normally this test runs as part of dist test, which only registers this test on platforms that support c-archive build mode, which includes all platforms that define these signals. But this doesn't help if you're just trying to type check everything in cmd. Add build constraints so that this package type checks on all platforms. Fixes #60164. Updates #37486. Change-Id: Id3f9ad4cc9f80146de16aedcf85d108a77215ae6 Reviewed-on: https://go-review.googlesource.com/c/go/+/494659 Reviewed-by: Bryan Mills <bcmills@google.com> Run-TryBot: Austin Clements <austin@google.com> Auto-Submit: Austin Clements <austin@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> |
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Austin Clements
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b26c3927bd |
cmd/dist: drop host test support
Host tests are used for emulated builders that use cross-compilation.
Today, this is the android-{386,amd64}-emu builders and all wasm
builders. These builders run all.bash on a linux/amd64 host to build
all packages and most tests for the emulated guest, and then run the
resulting test binaries inside the emulated guest. A small number of
test packages are “host tests”: these run on the host rather than the
guest because they invoke the Go toolchain themselves (which only
lives on the host) and run the resulting binaries in the guest.
However, this host test mechanism is barely used today, despite being
quite complex. This complexity is also causing significant friction to
implementing structured all.bash output.
As of this CL, the whole host test mechanism runs a total of 10 test
cases on a total of two builders (android-{386,amd64}-emu). There are
clearly several tests that are incorrectly being skipped, so we could
expand it to cover more test cases, but it would still apply to only
two builders. Furthermore, the two other Android builders
(android-{arm,arm64}-corellium) build the Go toolchain directly inside
Android and also have access to a C toolchain, so they are able to get
significantly better test coverage without the use of host tests. This
suggests that the android-*-emu builders could do the same. All of
these tests are cgo-related, so they don't run on the wasm hosts
anyway.
Given the incredibly low value of host tests today, they are not worth
their implementation complexity and the friction they cause. Hence,
this CL drops support for host tests. (This was also the last use of
rtSequential, so we drop support for sequential tests, too.)
Fixes #59999.
Change-Id: I3eaca853a8907abc8247709f15a0d19a872dd22d
Reviewed-on: https://go-review.googlesource.com/c/go/+/492986
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
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Austin Clements
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bf6c55a8b3 |
misc/cgo: move easy tests to cmd/cgo/internal
This moves most misc/cgo tests to cmd/cgo/internal. This is mostly a trivial rename and updating dist/test.go for the new paths, plus excluding these packages from regular dist test registration. A few tests were sensitive to what path they ran in, so we update those. This will let these tests access facilities in internal/testenv. For #37486. Change-Id: I3ed417c7c22d9b667f2767c0cb1f59118fcd4af6 Reviewed-on: https://go-review.googlesource.com/c/go/+/492720 Run-TryBot: Austin Clements <austin@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org> Reviewed-by: Bryan Mills <bcmills@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> |