1 //===-- thread_contention.cpp -----------------------------------*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "gwp_asan/tests/harness.h"
10 
11 // Note: Compilation of <atomic> and <thread> are extremely expensive for
12 // non-opt builds of clang.
13 #include <atomic>
14 #include <cstdlib>
15 #include <thread>
16 #include <vector>
17 
18 void asyncTask(gwp_asan::GuardedPoolAllocator *GPA,
19                std::atomic<bool> *StartingGun, unsigned NumIterations) {
20   while (!*StartingGun) {
21     // Wait for starting gun.
22   }
23 
24   // Get ourselves a new allocation.
25   for (unsigned i = 0; i < NumIterations; ++i) {
26     volatile char *Ptr = reinterpret_cast<volatile char *>(
27         GPA->allocate(GPA->maximumAllocationSize()));
28     // Do any other threads have access to this page?
29     EXPECT_EQ(*Ptr, 0);
30 
31     // Mark the page as from malloc. Wait to see if another thread also takes
32     // this page.
33     *Ptr = 'A';
34     std::this_thread::sleep_for(std::chrono::nanoseconds(10000));
35 
36     // Check we still own the page.
37     EXPECT_EQ(*Ptr, 'A');
38 
39     // And now release it.
40     *Ptr = 0;
41     GPA->deallocate(const_cast<char *>(Ptr));
42   }
43 }
44 
45 void runThreadContentionTest(unsigned NumThreads, unsigned NumIterations,
46                              gwp_asan::GuardedPoolAllocator *GPA) {
47 
48   std::atomic<bool> StartingGun{false};
49   std::vector<std::thread> Threads;
50   if (std::thread::hardware_concurrency() < NumThreads) {
51     NumThreads = std::thread::hardware_concurrency();
52   }
53 
54   for (unsigned i = 0; i < NumThreads; ++i) {
55     Threads.emplace_back(asyncTask, GPA, &StartingGun, NumIterations);
56   }
57 
58   StartingGun = true;
59 
60   for (auto &T : Threads)
61     T.join();
62 }
63 
64 TEST_F(CustomGuardedPoolAllocator, ThreadContention) {
65   unsigned NumThreads = 4;
66   unsigned NumIterations = 10000;
67   InitNumSlots(NumThreads);
68   runThreadContentionTest(NumThreads, NumIterations, &GPA);
69 }
70