[PATCH] D73055: [scudo][standalone] Allow sched_getaffinity to fail

[Kostya Kortchinsky via Phabricator via llvm-commits]

cryptoad updated this revision to Diff 239334.
cryptoad added a comment.

Commenting `getNumberOfCPUs` to indicate failure value in `common.h`,
moving `sched_getaffinity` comment in `linux.cpp` in body of function.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D73055/new/

https://reviews.llvm.org/D73055

Files:
  compiler-rt/lib/scudo/standalone/common.h
  compiler-rt/lib/scudo/standalone/linux.cpp
  compiler-rt/lib/scudo/standalone/tsd_shared.h


Index: compiler-rt/lib/scudo/standalone/tsd_shared.h
===================================================================
--- compiler-rt/lib/scudo/standalone/tsd_shared.h
+++ compiler-rt/lib/scudo/standalone/tsd_shared.h
@@ -18,7 +18,9 @@
   void initLinkerInitialized(Allocator *Instance) {
     Instance->initLinkerInitialized();
     CHECK_EQ(pthread_key_create(&PThreadKey, nullptr), 0); // For non-TLS
-    NumberOfTSDs = Min(Max(1U, getNumberOfCPUs()), MaxTSDCount);
+    const u32 NumberOfCPUs = getNumberOfCPUs();
+    NumberOfTSDs =
+        (NumberOfCPUs == 0) ? MaxTSDCount : Min(NumberOfCPUs, MaxTSDCount);
     TSDs = reinterpret_cast<TSD<Allocator> *>(
         map(nullptr, sizeof(TSD<Allocator>) * NumberOfTSDs, "scudo:tsd"));
     for (u32 I = 0; I < NumberOfTSDs; I++)
Index: compiler-rt/lib/scudo/standalone/linux.cpp
===================================================================
--- compiler-rt/lib/scudo/standalone/linux.cpp
+++ compiler-rt/lib/scudo/standalone/linux.cpp
@@ -132,7 +132,10 @@
 
 u32 getNumberOfCPUs() {
   cpu_set_t CPUs;
-  CHECK_EQ(sched_getaffinity(0, sizeof(cpu_set_t), &CPUs), 0);
+  // sched_getaffinity can fail for a variety of legitimate reasons (lack of
+  // CAP_SYS_NICE, syscall filtering, etc), in which case we shall return 0.
+  if (sched_getaffinity(0, sizeof(cpu_set_t), &CPUs) != 0)
+    return 0;
   return static_cast<u32>(CPU_COUNT(&CPUs));
 }
 
Index: compiler-rt/lib/scudo/standalone/common.h
===================================================================
--- compiler-rt/lib/scudo/standalone/common.h
+++ compiler-rt/lib/scudo/standalone/common.h
@@ -126,6 +126,7 @@
   return getPageSizeSlow();
 }
 
+// Returns 0 if the number of CPUs could not be determined.
 u32 getNumberOfCPUs();
 
 const char *getEnv(const char *Name);


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