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Commit d780dcba authored by Colin Cross's avatar Colin Cross
Browse files

Reduce logging around segfaults 

The excessive logging of pages with segfaults is making it hard to
see what caused the problem, only log the first page that segfaults,
the range that was being walked when the first segfault happened,
and the total number of pages that segfaulted.

Bug: 120032857
Test: memunreachable_test --gtest_filter=HeapWalkerTest.segv
Change-Id: I71821a3f5be65f2fbcb36afc4b7b1ffa4a48e660
parent 3a2bd498

libmemunreachable/HeapWalker.cpp

+15 −1
Original line number Diff line number Diff line
@@ -76,12 +76,14 @@ void HeapWalker::RecurseRoot(const Range& root) { 
    Range range = to_do.back();

    to_do.pop_back();



    walking_range_ = range;

    ForEachPtrInRange(range, [&](Range& ref_range, AllocationInfo* ref_info) {

      if (!ref_info->referenced_from_root) {

        ref_info->referenced_from_root = true;

        to_do.push_back(ref_range);

      }

    });

    walking_range_ = Range{0, 0};

  }

}
@@ -113,6 +115,10 @@ bool HeapWalker::DetectLeaks() { 


  RecurseRoot(vals);



  if (segv_page_count_ > 0) {

    MEM_ALOGE("%zu pages skipped due to segfaults", segv_page_count_);

  }



  return true;

}
@@ -168,7 +174,15 @@ void HeapWalker::HandleSegFault(ScopedSignalHandler& handler, int signal, siginf 
    handler.reset();

    return;

  }

  if (!segv_logged_) {

    MEM_ALOGW("failed to read page at %p, signal %d", si->si_addr, signal);

    if (walking_range_.begin != 0U) {

      MEM_ALOGW("while walking range %p-%p", reinterpret_cast<void*>(walking_range_.begin),

                reinterpret_cast<void*>(walking_range_.end));

    }

    segv_logged_ = true;

  }

  segv_page_count_++;

  if (!MapOverPage(si->si_addr)) {

    handler.reset();

  }

libmemunreachable/HeapWalker.h

+8 −2
Original line number Diff line number Diff line
@@ -53,7 +53,10 @@ class HeapWalker { 
        roots_(allocator),

        root_vals_(allocator),

        segv_handler_(),

        walking_ptr_(0) {

        walking_ptr_(0),

        walking_range_{0, 0},

        segv_logged_(false),

        segv_page_count_(0) {

    valid_allocations_range_.end = 0;

    valid_allocations_range_.begin = ~valid_allocations_range_.end;
@@ -100,7 +103,10 @@ class HeapWalker { 
  allocator::vector<uintptr_t> root_vals_;



  ScopedSignalHandler segv_handler_;

  uintptr_t walking_ptr_;

  volatile uintptr_t walking_ptr_;

  Range walking_range_;

  bool segv_logged_;

  size_t segv_page_count_;

};



template <class F>