[scudo] Add test exercising pthreads

[cryptoad]

Summary

Scudo didn't have any test using multiple threads. Add one, borrowed from lsan.

[alekseyshl]

What exactly are you testing here? That it does not crash? I do not see any checks.

[cryptoad]

Correct. Testing that it finishes properly without incidents.

[alekseyshl]

Please mention that explicitly in the top comment then.

Also, I don't think "Borrowed from lsan." adds any value. What does it mean, should we keep those tests in sync? I believe not, so, just remove it.

LGTM

[cryptoad]

Addressing Aleksey's comments.

[cryptoad]

Thank you Aleksey!

test/scudo/threads.cpp

+// RUN: %clang_scudo %s -o %t
+// RUN: SCUDO_OPTIONS="QuarantineSizeMb=0:ThreadLocalQuarantineSizeKb=0" %run %t 5 1000000 2>&1
+// RUN: SCUDO_OPTIONS="QuarantineSizeMb=1:ThreadLocalQuarantineSizeKb=64" %run %t 5 1000000 2>&1
+
+// Tests parallel allocations and deallocations of memory chunks from a number
+// of concurrent threads, with and without quarantine. Borrowed from lsan.
+
+#include <assert.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <sanitizer/allocator_interface.h>
+
+int num_threads;
+int total_num_alloc;
+const int kMaxNumThreads = 500;
+pthread_t tid[kMaxNumThreads];
+
+pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
+pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+bool go = false;
+
+void *thread_fun(void *arg) {
+  pthread_mutex_lock(&mutex);
+  while (!go) pthread_cond_wait(&cond, &mutex);
+  pthread_mutex_unlock(&mutex);
+  for (int i = 0; i < total_num_alloc / num_threads; i++) {
+    void *p = malloc(10);
+    __asm__ __volatile__("" : : "r"(p) : "memory");
+    free(p);
+  }
+  return 0;
+}
+
+int main(int argc, char** argv) {
+  assert(argc == 3);
+  num_threads = atoi(argv[1]);
+  assert(num_threads > 0);
+  assert(num_threads <= kMaxNumThreads);
+  total_num_alloc = atoi(argv[2]);
+  assert(total_num_alloc > 0);
+
+  printf("%d threads, %d allocations in each\n", num_threads,
+         total_num_alloc / num_threads);
+  fprintf(stderr, "Heap size before: %zd\n", __sanitizer_get_heap_size());
+  fprintf(stderr, "Allocated bytes before: %zd\n",
+          __sanitizer_get_current_allocated_bytes());
+
+  for (int i = 0; i < num_threads; i++)
+    pthread_create(&tid[i], 0, thread_fun, 0);
+  pthread_mutex_lock(&mutex);
+  go = true;
+  pthread_cond_broadcast(&cond);
+  pthread_mutex_unlock(&mutex);
+  for (int i = 0; i < num_threads; i++)
+    pthread_join(tid[i], 0);
+
+  fprintf(stderr, "Heap size after: %zd\n", __sanitizer_get_heap_size());
+  fprintf(stderr, "Allocated bytes after: %zd\n",
+          __sanitizer_get_current_allocated_bytes());
+
+  return 0;
+}