From edb4d95ddf8984ad5b24d964d45884977d2fde4b Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Mon, 13 Sep 2021 18:07:19 -0700 Subject: [PATCH] jit: Do not try to shut down LLVM state in case of LLVM triggered errors. If an allocation failed within LLVM it is not safe to call back into LLVM as LLVM is not generally safe against exceptions / stack-unwinding. Thus errors while in LLVM code are promoted to FATAL. However llvm_shutdown() did call back into LLVM even in such cases, while llvm_release_context() was careful not to do so. We cannot generally skip shutting down LLVM, as that can break profiling. But it's OK to do so if there was an error from within LLVM. Reported-By: Jelte Fennema Author: Andres Freund Author: Justin Pryzby Discussion: https://postgr.es/m/AM5PR83MB0178C52CCA0A8DEA0207DC14F7FF9@AM5PR83MB0178.EURPRD83.prod.outlook.com Backpatch: 11-, where jit was introduced --- src/backend/jit/llvm/llvmjit.c | 18 ++++++++++++++++-- src/backend/jit/llvm/llvmjit_error.cpp | 10 ++++++++++ src/include/jit/llvmjit.h | 1 + 3 files changed, 27 insertions(+), 2 deletions(-) diff --git a/src/backend/jit/llvm/llvmjit.c b/src/backend/jit/llvm/llvmjit.c index df691cbf1c5..169dad96d76 100644 --- a/src/backend/jit/llvm/llvmjit.c +++ b/src/backend/jit/llvm/llvmjit.c @@ -172,8 +172,6 @@ llvm_release_context(JitContext *context) { LLVMJitContext *llvm_context = (LLVMJitContext *) context; - llvm_enter_fatal_on_oom(); - /* * When this backend is exiting, don't clean up LLVM. As an error might * have occurred from within LLVM, we do not want to risk reentering. All @@ -182,6 +180,8 @@ llvm_release_context(JitContext *context) if (proc_exit_inprogress) return; + llvm_enter_fatal_on_oom(); + if (llvm_context->module) { LLVMDisposeModule(llvm_context->module); @@ -885,6 +885,20 @@ llvm_session_initialize(void) static void llvm_shutdown(int code, Datum arg) { + /* + * If llvm_shutdown() is reached while in a fatal-on-oom section an error + * has occurred in the middle of LLVM code. It is not safe to call back + * into LLVM (which is why a FATAL error was thrown). + * + * We do need to shutdown LLVM in other shutdown cases, otherwise + * e.g. profiling data won't be written out. + */ + if (llvm_in_fatal_on_oom()) + { + Assert(proc_exit_inprogress); + return; + } + #if LLVM_VERSION_MAJOR > 11 { if (llvm_opt3_orc) diff --git a/src/backend/jit/llvm/llvmjit_error.cpp b/src/backend/jit/llvm/llvmjit_error.cpp index 26bc828875e..daefb3e1fd9 100644 --- a/src/backend/jit/llvm/llvmjit_error.cpp +++ b/src/backend/jit/llvm/llvmjit_error.cpp @@ -83,6 +83,16 @@ llvm_leave_fatal_on_oom(void) } } +/* + * Are we currently in an fatal-on-oom section? Useful to skip cleanup in case + * of errors. + */ +bool +llvm_in_fatal_on_oom(void) +{ + return fatal_new_handler_depth > 0; +} + /* * Reset fatal error handling. This should only be called in error recovery * loops like PostgresMain()'s. diff --git a/src/include/jit/llvmjit.h b/src/include/jit/llvmjit.h index a8ba5a4facd..3560715e329 100644 --- a/src/include/jit/llvmjit.h +++ b/src/include/jit/llvmjit.h @@ -84,6 +84,7 @@ extern LLVMValueRef AttributeTemplate; extern void llvm_enter_fatal_on_oom(void); extern void llvm_leave_fatal_on_oom(void); +extern bool llvm_in_fatal_on_oom(void); extern void llvm_reset_after_error(void); extern void llvm_assert_in_fatal_section(void);