RSEQ related crashes since linux-6.19

### What The unit test `//tcmalloc/testing:background_test_no_glibc_rseq` reliably fails since the linux commit [39a167560a61 ("rseq: Optimize event setting")](https://github.com/torvalds/linux/commit/39a167560a61f913560ba803a96dbe6c15239f5c). This was discussed on [this archlinux issue](https://gitlab.archlinux.org/archlinux/packaging/packages/linux/-/issues/185). It was also [discussed on the kernel mailing list](https://lore.kernel.org/all/CALzav=fcN17cxdKseGAGHveTVYZNJwbEL6za6+DbKp-uiZwaOg@mail.gmail.com/). The latter thread also says: > Is this using tcmalloc? If so, that is somewhat expected because tcmalloc is known to violate upstream rseq ABI. IIRC you should get a nice splat if you enable rseq debug mode (echo 1 > /debug/rseq/debug). > > Perhaps this is the nudge Google needs to go fix this. ### Failing unit test: ```bash [arch@podman-mongodb tcmalloc]$ GLIBC_TUNABLES=glibc.pthread.rseq=1 bazel-bin/tcmalloc/testing/background_test_no_glibc_rseq [==========] Running 2 tests from 1 test suite. [----------] Global test environment set-up. [----------] 2 tests from BackgroundTest [ RUN ] BackgroundTest.Defaults [ OK ] BackgroundTest.Defaults (0 ms) [ RUN ] BackgroundTest.Stress [ OK ] BackgroundTest.Stress (10017 ms) [----------] 2 tests from BackgroundTest (10018 ms total) [----------] Global test environment tear-down [==========] 2 tests from 1 test suite ran. (10018 ms total) [ PASSED ] 2 tests. [arch@podman-mongodb tcmalloc]$ GLIBC_TUNABLES=glibc.pthread.rseq=0 bazel-bin/tcmalloc/testing/background_test_no_glibc_rseq [==========] Running 2 tests from 1 test suite. [----------] Global test environment set-up. [----------] 2 tests from BackgroundTest [ RUN ] BackgroundTest.Defaults [ OK ] BackgroundTest.Defaults (0 ms) [ RUN ] BackgroundTest.Stress 14207 ./tcmalloc/internal/percpu_tcmalloc.h:852] CHECK in Pop: next (false) Aborted (core dumped) GLIBC_TUNABLES=glibc.pthread.rseq=0 bazel-bin/tcmalloc/testing/background_test_no_glibc_rseq [arch@podman-mongodb tcmalloc]$ GLIBC_TUNABLES=glibc.pthread.rseq=0 /tmp/bazel test //tcmalloc/testing:background_test_no_glibc_rseq WARNING: Build option --test_env has changed, discarding analysis cache (this can be expensive, see https://bazel.build/advanced/performance/iteration-speed). INFO: Analyzed target //tcmalloc/testing:background_test_no_glibc_rseq (0 packages loaded, 5304 targets configured). FAIL: //tcmalloc/testing:background_test_no_glibc_rseq (Aborted) (see /home/arch/.cache/bazel/_bazel_arch/3c882abdfeb0a7dc4942cd1a7209754a/execroot/_main/bazel-out/k8-fastbuild/testlogs/tcmalloc/testing/background_test_no_glibc_rseq/test.log) INFO: Found 1 test target... Target //tcmalloc/testing:background_test_no_glibc_rseq up-to-date: bazel-bin/tcmalloc/testing/background_test_no_glibc_rseq INFO: Elapsed time: 3.948s, Critical Path: 1.62s INFO: 2 processes: 644 action cache hit, 2 linux-sandbox. INFO: Build completed, 1 test FAILED, 2 total actions //tcmalloc/testing:background_test_no_glibc_rseq FAILED in 1.6s /home/arch/.cache/bazel/_bazel_arch/3c882abdfeb0a7dc4942cd1a7209754a/execroot/_main/bazel-out/k8-fastbuild/testlogs/tcmalloc/testing/background_test_no_glibc_rseq/test.log Executed 1 out of 1 test: 1 fails locally. [arch@podman-mongodb tcmalloc]$ cat /home/arch/.cache/bazel/_bazel_arch/3c882abdfeb0a7dc4942cd1a7209754a/execroot/_main/bazel-out/k8-fastbuild/testlogs/tcmalloc/testing/background_test_no_glibc_rseq/test.log exec ${PAGER:-/usr/bin/less} "$0" || exit 1 Executing tests from //tcmalloc/testing:background_test_no_glibc_rseq ----------------------------------------------------------------------------- [==========] Running 2 tests from 1 test suite. [----------] Global test environment set-up. [----------] 2 tests from BackgroundTest [ RUN ] BackgroundTest.Defaults [ OK ] BackgroundTest.Defaults (0 ms) [ RUN ] BackgroundTest.Stress 28 ./tcmalloc/internal/percpu_tcmalloc.h:852] CHECK in Pop: next (false) *** SIGABRT received at time=1773167104 on cpu 1 *** 23 ./tcmalloc/internal/percpu_tcmalloc.h:852] CHECK in Pop: next (false) [failure_signal_handler.cc : 377] RAW: Signal 6 raised at PC=0x7f7d81d89a2c while already in AbslFailureSignalHandler() 19 ./tcmalloc/internal/percpu_tcmalloc.h:852] CHECK in Pop: next (false) [failure_signal_handler.cc : 377] RAW: Signal 6 raised at PC=0x7f7d81d89a2c while already in AbslFailureSignalHandler() [failure_signal_handler.cc : 377] RAW: Signal 11 raised at PC=0x5580fdd87519 while already in AbslFailureSignalHandler() [failure_signal_handler.cc : 377] RAW: Signal 11 raised at PC=0x5580fdd87519 while already in AbslFailureSignalHandler() 20 ./tcmalloc/internal/percpu_tcmalloc.h:852] CHECK in Pop: next (false) [failure_signal_handler.cc : 377] RAW: Signal 6 raised at PC=0x7f7d81d89a2c while already in AbslFailureSignalHandler() PC: @ 0x7f7d81d89a2c (unknown) (unknown) @ 0x7f7d82ae1c35 64 absl::lts_20260107::WriteFailureInfo() @ 0x7f7d82ae1e74 96 absl::lts_20260107::AbslFailureSignalHandler() @ 0x7f7d81d2f2d0 3120 (unknown) @ 0x7f7d81d2f1a0 32 raise @ 0x7f7d81d165fe 192 abort @ 0x7f7d826b2d8d 704 tcmalloc::tcmalloc_internal::Crash() @ 0x7f7d826b2dc2 48 tcmalloc::tcmalloc_internal::CheckFailed() @ 0x5580fdc850a2 640 tcmalloc::tcmalloc_internal::CheckFailed<>() @ 0x5580fdd78ab6 368 operator new() @ 0x5580fdb7bc44 64 std::__new_allocator<>::allocate() @ 0x5580fdb7a3a3 48 std::_Vector_base<>::_M_allocate() @ 0x5580fdb7a5d1 256 std::vector<>::_M_realloc_append<>() @ 0x5580fdb7934a 128 std::vector<>::emplace_back<>() @ 0x5580fdb77c6d 48 std::vector<>::push_back() @ 0x5580fdb76395 208 tcmalloc::AllocatorHarness::Run() @ 0x5580fdb73d9d 32 tcmalloc::(anonymous namespace)::BackgroundTest_Stress_Test::TestBody()::{lambda()#1}::operator()() @ 0x5580fdb74466 48 std::__invoke_impl<>() @ 0x5580fdb74354 48 std::__invoke_r<>() @ 0x5580fdb7421b 64 std::_Function_handler<>::_M_invoke() @ 0x5580fdb78128 32 std::function<>::operator()() @ 0x5580fdb76b50 32 tcmalloc::ThreadManager::Start()::{lambda()#1}::operator()() @ 0x5580fdb7eba2 48 std::__invoke_impl<>() @ 0x5580fdb7eaf2 48 std::__invoke<>() @ 0x5580fdb7ea49 64 std::thread::_Invoker<>::_M_invoke<>() @ 0x5580fdb7e9e6 32 std::thread::_Invoker<>::operator()() @ 0x5580fdb7e9aa 32 std::thread::_State_impl<>::_M_run() @ 0x7f7d820e55a4 32 (unknown) @ 0x7f7d81d8797a 224 (unknown) @ 0x7f7d81e0b2bc (unknown) (unknown) ```