[scudo] Allow to specify the maximum number of TSDs at compile time

Summary:
This introduces `SCUDO_MAX_CACHES` allowing to define an upper bound to the
number of `ScudoTSD` created in the Shared TSD model (by default 32U).
This name felt clearer than `SCUDO_MAX_TSDS` which is technically what it really
is. I am opened to suggestions if that doesn't feel right.

Additionally change `getNumberOfCPUs` to return a `u32` to be more consistent.

Reviewers: alekseyshl

Reviewed By: alekseyshl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D39338

llvm-svn: 316788

compiler-rt/lib/scudo/scudo_platform.h

@@ -40,6 +40,11 @@
 # error "The exclusive TSD model is not supported on this platform."
 #endif
 
+// Maximum number of TSDs that can be created for the Shared model.
+#ifndef SCUDO_SHARED_TSD_POOL_SIZE
+# define SCUDO_SHARED_TSD_POOL_SIZE 32U
+#endif  // SCUDO_SHARED_TSD_POOL_SIZE
+
 namespace __scudo {
 
 #if SANITIZER_CAN_USE_ALLOCATOR64

compiler-rt/lib/scudo/scudo_tsd_shared.cpp

@@ -25,7 +25,7 @@ static ScudoTSD *TSDs;
 static u32 NumberOfTSDs;
 
 // sysconf(_SC_NPROCESSORS_{CONF,ONLN}) cannot be used as they allocate memory.
-static uptr getNumberOfCPUs() {
+static u32 getNumberOfCPUs() {
   cpu_set_t CPUs;
   CHECK_EQ(sched_getaffinity(0, sizeof(cpu_set_t), &CPUs), 0);
   return CPU_COUNT(&CPUs);
@@ -34,11 +34,8 @@ static uptr getNumberOfCPUs() {
 static void initOnce() {
   CHECK_EQ(pthread_key_create(&PThreadKey, NULL), 0);
   initScudo();
-  NumberOfTSDs = getNumberOfCPUs();
-  if (NumberOfTSDs == 0)
-    NumberOfTSDs = 1;
-  if (NumberOfTSDs > 32)
-    NumberOfTSDs = 32;
+  NumberOfTSDs = Min(Max(1U, getNumberOfCPUs()),
+                     static_cast<u32>(SCUDO_SHARED_TSD_POOL_SIZE));
   TSDs = reinterpret_cast<ScudoTSD *>(
       MmapOrDie(sizeof(ScudoTSD) * NumberOfTSDs, "ScudoTSDs"));
   for (u32 i = 0; i < NumberOfTSDs; i++)