Handle EAGAIN error for the mincore syscall used

base/trace_event/process_memory_dump.cc

Index: base/trace_event/process_memory_dump.cc
diff --git a/base/trace_event/process_memory_dump.cc b/base/trace_event/process_memory_dump.cc
index 0ec007e2ee46f5140bf83ee5580a7f5c1ee221f4..36a317d00deb45dcec8300812ffdee1483ecfc3a 100644
--- a/base/trace_event/process_memory_dump.cc
+++ b/base/trace_event/process_memory_dump.cc
@@ -51,14 +51,32 @@ size_t ProcessMemoryDump::CountResidentBytes(void* start_address,
 
 #if defined(OS_MACOSX) || defined(OS_IOS)
     std::vector<char> vec(page_count + 1);
+    // mincore in MAC does not fail with EAGAIN.
     int res = mincore(chunk_start, chunk_size, vector_as_array(&vec));
     DCHECK(!res);
+    if (res) {
+      LOG(ERROR)
+          << "Mincore call failed. The resident size may not be accurate";

[Primiano Tucci (use gerrit), 2015/10/15 11:20:18]

nit: s/Mincore/mincore()/
also, if you continue here it will not be non-accurate, it will be 0.

[ssid, 2015/10/15 11:23:43]

The call to mincore failed only once. The next set of pages could pass and give
some value. So, mentioned not accurate.

+      continue;
+    }
+
     for (size_t i = 0; i < page_count; i++)
       resident_page_count += vec[i] & MINCORE_INCORE ? 1 : 0;
 #else   // defined(OS_MACOSX) || defined(OS_IOS)
     std::vector<unsigned char> vec(page_count + 1);
-    int res = mincore(chunk_start, chunk_size, vector_as_array(&vec));
+    int error_counter = 0;
+    int res = 0;
+    // HANDLE_EINTR tries for 100 times. So following the same pattern.
+    do {
+      res = mincore(chunk_start, chunk_size, vector_as_array(&vec));
+    } while (res == -1 && errno == EAGAIN && error_counter++ < 100);
     DCHECK(!res);
+    if (res) {
+      LOG(ERROR)
+          << "Mincore call failed. The resident size may not be accurate";

[Primiano Tucci (use gerrit), 2015/10/15 11:20:18]

can we avoid duplicating this and above?

[ssid, 2015/10/15 11:23:43]

I would have to add 3 extra #if defined. that is why duplicating.

[Primiano Tucci (use gerrit), 2015/10/15 11:27:13]

??
how about you just add this to before line 87:

DCHECK_EQ(0, res);
if (res) {
  LOG(ERROR)<< "mincore() call failed. The resident size may not be accurate";
 total_resident_size = 0;
}

[ssid, 2015/10/15 11:39:30]

Yes, sounds good.

+      continue;
+    }
+
     for (size_t i = 0; i < page_count; i++)
       resident_page_count += vec[i];
 #endif  // defined(OS_MACOSX) || defined(OS_IOS)