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test: add tcache_fiber_migration standalone LTO reproducer

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Exercises the tsd thread-pointer hoisting bug: ucontext fibers do
free/swapcontext/malloc in one frame on a worker pool, so a fiber routinely
resumes on a different OS thread; under whole-program LTO the inlined fastpath
then frees/allocs against the previous thread's tcache and crashes.

It is a standalone program (no test harness, so it can be static-linked without
symbol clashes), calling jemalloc via JEMALLOC_MANGLE and linked statically with
--whole-archive so the allocator inlines next to the swapcontext.  Built only
when -flto is in the build flags -- without LTO the allocator is not inlined and
the bug cannot reproduce, so the test would be a meaningless always-pass -- and
gated on ELF + static + have_ucontext (a configure link test, since musl
declares but does not implement getcontext/makecontext/swapcontext).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Azat Khuzhin 2026-06-22 12:47:46 +02:00
parent 9f37c70826
commit c68b7b1cac
3 changed files with 181 additions and 0 deletions
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27
Makefile.in
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@ -59,6 +59,7 @@ enable_autogen := @enable_autogen@
enable_doc := @enable_doc@
enable_shared := @enable_shared@
enable_static := @enable_static@
have_ucontext := @have_ucontext@
enable_prof := @enable_prof@
enable_zone_allocator := @enable_zone_allocator@
enable_experimental_smallocx := @enable_experimental_smallocx@
@ -345,6 +346,24 @@ ifeq (@enable_experimental_smallocx@, 1)
TESTS_INTEGRATION += \
$(srcroot)test/integration/smallocx.c
endif
# tcache_fiber_migration is a standalone LTO reproducer (issue #2890): the
# dedicated rule below links it against the static archive (--whole-archive) so
# the allocator fastpath inlines next to the swapcontext. It needs the static
# archive, GNU-ld --whole-archive semantics (the ELF gate), and working
# ucontext fibers -- have_ucontext is a configure link test because musl
# declares getcontext/makecontext/swapcontext but does not implement them, so
# the ELF gate alone would break `make check` on Alpine/musl. Built only when
# the build uses LTO (-flto in CFLAGS): without inlining across the swapcontext
# the bug cannot reproduce.
ifeq (elf, $(ABI))
ifeq ($(enable_static), 1)
ifeq (1, $(have_ucontext))
ifneq (,$(findstring -flto,$(CFLAGS)))
TESTS_INTEGRATION += $(srcroot)test/integration/tcache_fiber_migration.c
endif
endif
endif
endif
ifeq (@enable_cxx@, 1)
CPP_SRCS := $(srcroot)src/jemalloc_cpp.cpp
TESTS_INTEGRATION_CPP := $(srcroot)test/integration/cpp/basic.cpp
@ -578,6 +597,14 @@ $(objroot)test/integration/%$(EXE): $(objroot)test/integration/%.$(O) $(C_TESTLI
@mkdir -p $(@D)
$(CC) $(TEST_LD_MODE) $(LDTARGET) $(filter %.$(O),$^) $(call RPATH,$(objroot)lib) $(LJEMALLOC) $(LDFLAGS) $(filter-out -lm,$(filter -lrt -pthread -lstdc++,$(LIBS))) $(LM) $(EXTRA_LDFLAGS)
# tcache_fiber_migration (issue #2890) must inline the allocator next to the
# swapcontext, so link jemalloc statically (--whole-archive), without the test
# harness/shared lib; whole-program LTO (from the build's flags) does the
# inlining. Explicit rule -- overrides the generic integration rule above.
$(objroot)test/integration/tcache_fiber_migration$(EXE): $(objroot)test/integration/tcache_fiber_migration.$(O) $(objroot)lib/$(LIBJEMALLOC).$(A)
@mkdir -p $(@D)
$(CC) $(LDTARGET) $(objroot)test/integration/tcache_fiber_migration.$(O) -Wl,--whole-archive $(objroot)lib/$(LIBJEMALLOC).$(A) -Wl,--no-whole-archive $(LDFLAGS) -pthread $(filter-out -lm,$(LIBS)) $(LM) $(EXTRA_LDFLAGS)
$(objroot)test/integration/cpp/%$(EXE): $(objroot)test/integration/cpp/%.$(O) $(C_TESTLIB_INTEGRATION_OBJS) $(C_UTIL_INTEGRATION_OBJS) $(objroot)lib/$(LIBJEMALLOC).$(IMPORTLIB)
@mkdir -p $(@D)
$(CXX) $(LDTARGET) $(filter %.$(O),$^) $(call RPATH,$(objroot)lib) $(objroot)lib/$(LIBJEMALLOC).$(IMPORTLIB) $(LDFLAGS) $(filter-out -lm,$(LIBS)) -lm $(EXTRA_LDFLAGS)