[Openmp-commits] [openmp] [Libomptarget] Fix data mapping on dynamic loads (PR #80559)

[Joseph Huber via Openmp-commits]

https://github.com/jhuber6 created https://github.com/llvm/llvm-project/pull/80559

Summary:
The current logic tries to map target mapping tables to the current
device. Right now it assumes that data is only mapped a single time per
device. This is only true if we have a single instance of the runtime
running on a single program. However, in the case of dynamic library
loads or shared libraries, this may happen multiple times.

Given a case of a simple dynamic library load which has its own target
kernel instruction, the current logic had only the first call to
`__tgt_target_kernel` to the data mapping for that device. Then, when
the next dynamic library load got called, it would see that the global
were already mapped for that device and skip registering its own
entires, even though they were distinct. This resulted in none of the
mappings being done and hitting an assertion.

This patch simply gets rid of this per-device check. The check should
instead be on the host offloading entries. We already have logic that
calls `continue` if we already have entries for that pointer, so we can
simply rely on that instead.


>From 88b88c2dff6f1f9548bef0259c72de19b4bda491 Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Sat, 3 Feb 2024 13:36:08 -0600
Subject: [PATCH] [Libomptarget] Fix data mapping on dynamic loads

Summary:
The current logic tries to map target mapping tables to the current
device. Right now it assumes that data is only mapped a single time per
device. This is only true if we have a single instance of the runtime
running on a single program. However, in the case of dynamic library
loads or shared libraries, this may happen multiple times.

Given a case of a simple dynamic library load which has its own target
kernel instruction, the current logic had only the first call to
`__tgt_target_kernel` to the data mapping for that device. Then, when
the next dynamic library load got called, it would see that the global
were already mapped for that device and skip registering its own
entires, even though they were distinct. This resulted in none of the
mappings being done and hitting an assertion.

This patch simply gets rid of this per-device check. The check should
instead be on the host offloading entries. We already have logic that
calls `continue` if we already have entries for that pointer, so we can
simply rely on that instead.
---
 openmp/libomptarget/include/device.h                      | 2 --
 openmp/libomptarget/src/omptarget.cpp                     | 5 -----
 openmp/libomptarget/test/offloading/dynamic_module_load.c | 3 +++
 3 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/openmp/libomptarget/include/device.h b/openmp/libomptarget/include/device.h
index 3b40de959533b..bd2829722bb32 100644
--- a/openmp/libomptarget/include/device.h
+++ b/openmp/libomptarget/include/device.h
@@ -43,8 +43,6 @@ struct DeviceTy {
   PluginAdaptorTy *RTL;
   int32_t RTLDeviceID;
 
-  bool HasMappedGlobalData = false;
-
   DeviceTy(PluginAdaptorTy *RTL, int32_t DeviceID, int32_t RTLDeviceID);
   // DeviceTy is not copyable
   DeviceTy(const DeviceTy &D) = delete;
diff --git a/openmp/libomptarget/src/omptarget.cpp b/openmp/libomptarget/src/omptarget.cpp
index 5b852495b7501..74e23b06340c0 100644
--- a/openmp/libomptarget/src/omptarget.cpp
+++ b/openmp/libomptarget/src/omptarget.cpp
@@ -132,9 +132,6 @@ static uint64_t getPartialStructRequiredAlignment(void *HstPtrBase) {
 
 /// Map global data and execute pending ctors
 static int initLibrary(DeviceTy &Device) {
-  if (Device.HasMappedGlobalData)
-    return OFFLOAD_SUCCESS;
-
   /*
    * Map global data
    */
@@ -294,8 +291,6 @@ static int initLibrary(DeviceTy &Device) {
   if (Rc != OFFLOAD_SUCCESS)
     return Rc;
 
-  Device.HasMappedGlobalData = true;
-
   static Int32Envar DumpOffloadEntries =
       Int32Envar("OMPTARGET_DUMP_OFFLOAD_ENTRIES", -1);
   if (DumpOffloadEntries.get() == DeviceId)
diff --git a/openmp/libomptarget/test/offloading/dynamic_module_load.c b/openmp/libomptarget/test/offloading/dynamic_module_load.c
index 935d402ef2be1..5393f33e84f85 100644
--- a/openmp/libomptarget/test/offloading/dynamic_module_load.c
+++ b/openmp/libomptarget/test/offloading/dynamic_module_load.c
@@ -12,6 +12,9 @@ int foo() {
 #include <dlfcn.h>
 #include <stdio.h>
 int main(int argc, char **argv) {
+#pragma omp target
+  ;
+
   void *Handle = dlopen(argv[1], RTLD_NOW);
   int (*Foo)(void);