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| author | Ian Lance Taylor <ian@gcc.gnu.org> | 2018-12-29 00:07:06 +0000 |
|---|---|---|
| committer | Ian Lance Taylor <ian@gcc.gnu.org> | 2018-12-29 00:07:06 +0000 |
| commit | e20bfbd18e64b8ab9428aa518b5d7b74a73461d9 (patch) | |
| tree | a5200fb4bd7b40981b58590f089defa85c251512 | |
| parent | 50bec22834e0b147fca92bea80501bccc309ce4d (diff) | |
| download | gcc-e20bfbd18e64b8ab9428aa518b5d7b74a73461d9.zip gcc-e20bfbd18e64b8ab9428aa518b5d7b74a73461d9.tar.gz gcc-e20bfbd18e64b8ab9428aa518b5d7b74a73461d9.tar.bz2 | |
runtime: prevent deadlock when profiling signal arrives in stack scan
Precise stack scan needs to unwind the stack. When it is
unwinding the stack, if a profiling signal arrives, which also
does a traceback, it may deadlock in dl_iterate_phdr. Prevent
this deadlock by setting up runtime_in_callers before traceback.
Reviewed-on: https://go-review.googlesource.com/c/155766
From-SVN: r267457
| -rw-r--r-- | gcc/go/gofrontend/MERGE | 2 | ||||
| -rw-r--r-- | libgo/runtime/go-callers.c | 8 | ||||
| -rw-r--r-- | libgo/runtime/go-unwind.c | 2 | ||||
| -rw-r--r-- | libgo/runtime/runtime.h | 6 |
4 files changed, 13 insertions, 5 deletions
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE index 2552025..a36396c 100644 --- a/gcc/go/gofrontend/MERGE +++ b/gcc/go/gofrontend/MERGE @@ -1,4 +1,4 @@ -d9a30434440469c640a120fe7132057f5644d38c +0e482bef69d73b9381dbc543e200a1fe57275e81 The first line of this file holds the git revision number of the last merge done from the gofrontend repository. diff --git a/libgo/runtime/go-callers.c b/libgo/runtime/go-callers.c index b16ae0c..78ada7a 100644 --- a/libgo/runtime/go-callers.c +++ b/libgo/runtime/go-callers.c @@ -16,7 +16,7 @@ older versions of glibc when a SIGPROF signal arrives while collecting a backtrace. */ -static uint32 runtime_in_callers; +uint32 __go_runtime_in_callers; /* Argument passed to callback function. */ @@ -185,7 +185,7 @@ bool alreadyInCallers(void) bool alreadyInCallers() { - return runtime_atomicload(&runtime_in_callers) > 0; + return runtime_atomicload(&__go_runtime_in_callers) > 0; } /* Gather caller PC's. */ @@ -203,9 +203,9 @@ runtime_callers (int32 skip, Location *locbuf, int32 m, bool keep_thunks) data.max = m; data.keep_thunks = keep_thunks; state = __go_get_backtrace_state (); - runtime_xadd (&runtime_in_callers, 1); + runtime_xadd (&__go_runtime_in_callers, 1); backtrace_full (state, 0, callback, error_callback, &data); - runtime_xadd (&runtime_in_callers, -1); + runtime_xadd (&__go_runtime_in_callers, -1); /* For some reason GCC sometimes loses the name of a thunk function at the top of the stack. If we are skipping thunks, skip that diff --git a/libgo/runtime/go-unwind.c b/libgo/runtime/go-unwind.c index 58cb270..158cbd0 100644 --- a/libgo/runtime/go-unwind.c +++ b/libgo/runtime/go-unwind.c @@ -792,7 +792,9 @@ bool scanstackwithmap (void *gcw) { _Unwind_Reason_Code code; + runtime_xadd (&__go_runtime_in_callers, 1); code = _Unwind_Backtrace (scanstackwithmap_callback, gcw); + runtime_xadd (&__go_runtime_in_callers, -1); return code == _URC_END_OF_STACK; } diff --git a/libgo/runtime/runtime.h b/libgo/runtime/runtime.h index 21921ec..9f6e251 100644 --- a/libgo/runtime/runtime.h +++ b/libgo/runtime/runtime.h @@ -515,3 +515,9 @@ bool runtime_usestackmaps; bool probestackmaps(void) __asm__("runtime.probestackmaps"); + +// This is set to non-zero when calling backtrace_full. This is used +// to avoid getting hanging on a recursive lock in dl_iterate_phdr on +// older versions of glibc when a SIGPROF signal arrives while +// collecting a backtrace. +extern uint32 __go_runtime_in_callers; |