Investigate usleep failure on Linux. Add more debug output.

src/platform-linux.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 810 matching lines @@
         vm_tid_(syscall(SYS_gettid)),
         signal_sender_launched_(false) {
   }
 
   void SignalSender() {
     while (sampler_->IsActive()) {
       // Glibc doesn't provide a wrapper for tgkill(2).
       syscall(SYS_tgkill, vm_tgid_, vm_tid_, SIGPROF);
       // Convert ms to us and subtract 100 us to compensate delays
       // occuring during signal delivery.
-      int result = usleep(sampler_->interval_ * 1000 - 100);
-      ASSERT(result == 0 || errno == EINTR);
+      const useconds_t interval = sampler_->interval_ * 1000 - 100;
+      int result = usleep(interval);
+#ifdef DEBUG
+      if (result != 0 && errno != EINTR) {
+        fprintf(stderr,
+                "SignalSender usleep error; interval = %u, errno = %d\n",
+                interval,
+                errno);
+        ASSERT(result == 0 || errno == EINTR);
+      }
+#endif
       USE(result);
     }
   }
 
   Sampler* sampler_;
   bool signal_handler_installed_;
   struct sigaction old_signal_handler_;
   int vm_tgid_;
   int vm_tid_;
   bool signal_sender_launched_;
@@ skipping 12 matching lines @@
 Sampler::Sampler(int interval, bool profiling)
     : interval_(interval),
       profiling_(profiling),
       synchronous_(profiling),
       active_(false) {
   data_ = new PlatformData(this);
 }
 
 
 Sampler::~Sampler() {
+  ASSERT(!data_->signal_sender_launched_);
   delete data_;
 }
 
 
 void Sampler::Start() {
   // There can only be one active sampler at the time on POSIX
   // platforms.
   if (active_sampler_ != NULL) return;
 
   // Request profiling signals.
@@ skipping 35 matching lines @@
   }
 
   // This sampler is no longer the active sampler.
   active_sampler_ = NULL;
 }
 
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal