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Enable per thread register state cache on libunwind #55049

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merged 4 commits into from
Jul 31, 2024
+81 −27
Merged

Enable per thread register state cache on libunwind #55049

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6dc43b6
Enable per thread register state cache on libunwind
andrebsguedes Jul 5, 2024
267d0dc
Include function to ensure tls allocation in the patch and call it fr…
andrebsguedes Jul 23, 2024
9ce5f76
Bump LibUnwind_jll to v1.8.1+1 to enable per thread caches
andrebsguedes Jul 24, 2024
c4d71d9
Only ensure tls when libunwind is present
andrebsguedes Jul 24, 2024
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44 changes: 44 additions & 0 deletions deps/patches/libunwind-disable-initial-exec-tls.patch
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Does it make sense to upstream this patch?

Original file line number Diff line number Diff line change
@@ -0,0 +1,44 @@
diff --git a/include/libunwind-common.h.in b/include/libunwind-common.h.in
index 893fdd69..80ab9648 100644
--- a/include/libunwind-common.h.in
+++ b/include/libunwind-common.h.in
@@ -340,5 +340,6 @@ extern int unw_get_elf_filename_by_ip (unw_addr_space_t, unw_word_t, char *,
extern const char *unw_strerror (int);
extern int unw_backtrace (void **, int);
extern int unw_backtrace2 (void **, int, unw_context_t*, int);
+extern int unw_ensure_tls (void);

extern unw_addr_space_t unw_local_addr_space;
diff --git a/src/dwarf/Gparser.c b/src/dwarf/Gparser.c
index 7a5d7e1f..8453ffb0 100644
--- a/src/dwarf/Gparser.c
+++ b/src/dwarf/Gparser.c
@@ -623,7 +623,7 @@ get_rs_cache (unw_addr_space_t as, intrmask_t *saved_maskp)
#if defined(HAVE___CACHE_PER_THREAD) && HAVE___CACHE_PER_THREAD
if (likely (caching == UNW_CACHE_PER_THREAD))
{
- static _Thread_local struct dwarf_rs_cache tls_cache __attribute__((tls_model("initial-exec")));
+ static _Thread_local struct dwarf_rs_cache tls_cache;
Debug (16, "using TLS cache\n");
cache = &tls_cache;
}
diff --git a/src/mi/init.c b/src/mi/init.c
index e4431eeb..07cae852 100644
--- a/src/mi/init.c
+++ b/src/mi/init.c
@@ -82,3 +82,15 @@ mi_init (void)
unw_init_page_size();
assert(sizeof(struct cursor) <= sizeof(unw_cursor_t));
}
+
+int
+unw_ensure_tls (void)
+{
+#if defined(HAVE___CACHE_PER_THREAD) && HAVE___CACHE_PER_THREAD
+ static _Thread_local int alloc_trigger;
+ alloc_trigger = 1;
+ return alloc_trigger;
+#else
+ return 0;
+#endif
+}
8 changes: 6 additions & 2 deletions deps/unwind.mk
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Original file line number Diff line number Diff line change
Expand Up @@ -38,13 +38,17 @@ $(SRCCACHE)/libunwind-$(UNWIND_VER)/libunwind-aarch64-inline-asm.patch-applied:
cd $(SRCCACHE)/libunwind-$(UNWIND_VER) && patch -p1 -f -u -l < $(SRCDIR)/patches/libunwind-aarch64-inline-asm.patch
echo 1 > $@

$(SRCCACHE)/libunwind-$(UNWIND_VER)/libunwind-disable-initial-exec-tls.patch-applied: $(SRCCACHE)/libunwind-$(UNWIND_VER)/libunwind-aarch64-inline-asm.patch-applied
cd $(SRCCACHE)/libunwind-$(UNWIND_VER) && patch -p1 -f -u -l < $(SRCDIR)/patches/libunwind-disable-initial-exec-tls.patch
echo 1 > $@

# note minidebuginfo requires liblzma, which we do not have a source build for
# (it will be enabled in BinaryBuilder-based downloads however)
# since https://github.com/JuliaPackaging/Yggdrasil/commit/0149e021be9badcb331007c62442a4f554f3003c
$(BUILDDIR)/libunwind-$(UNWIND_VER)/build-configured: $(SRCCACHE)/libunwind-$(UNWIND_VER)/source-extracted $(SRCCACHE)/libunwind-$(UNWIND_VER)/libunwind-aarch64-inline-asm.patch-applied
$(BUILDDIR)/libunwind-$(UNWIND_VER)/build-configured: $(SRCCACHE)/libunwind-$(UNWIND_VER)/source-extracted $(SRCCACHE)/libunwind-$(UNWIND_VER)/libunwind-disable-initial-exec-tls.patch-applied
mkdir -p $(dir $@)
cd $(dir $@) && \
$(dir $<)/configure $(CONFIGURE_COMMON) CPPFLAGS="$(CPPFLAGS) $(LIBUNWIND_CPPFLAGS)" CFLAGS="$(CFLAGS) $(LIBUNWIND_CFLAGS)" --enable-shared --disable-minidebuginfo --disable-tests --enable-zlibdebuginfo --disable-conservative-checks
$(dir $<)/configure $(CONFIGURE_COMMON) CPPFLAGS="$(CPPFLAGS) $(LIBUNWIND_CPPFLAGS)" CFLAGS="$(CFLAGS) $(LIBUNWIND_CFLAGS)" --enable-shared --disable-minidebuginfo --disable-tests --enable-zlibdebuginfo --disable-conservative-checks --enable-per-thread-cache
echo 1 > $@

$(BUILDDIR)/libunwind-$(UNWIND_VER)/build-compiled: $(BUILDDIR)/libunwind-$(UNWIND_VER)/build-configured
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6 changes: 6 additions & 0 deletions src/threading.c
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Original file line number Diff line number Diff line change
Expand Up @@ -404,6 +404,12 @@ jl_ptls_t jl_init_threadtls(int16_t tid)
jl_fence();
uv_mutex_unlock(&tls_lock);

#if !defined(JL_DISABLE_LIBUNWIND)
// ensures libunwind TLS space for this thread is allocated eagerly
// to make unwinding async-signal-safe even when using thread local caches.
unw_ensure_tls();
#endif

return ptls;
}

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