13 files changed, 236 insertions, 29 deletions

diff --git a/absl/base/internal/spinlock_linux.inc b/absl/base/internal/spinlock_linux.inc
index 94c861dc6ca2..3bbd4954f1ed 100644
--- a/absl/base/internal/spinlock_linux.inc
+++ b/absl/base/internal/spinlock_linux.inc
@@ -51,17 +51,12 @@ extern "C" {
 ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockDelay(
     std::atomic<uint32_t> *w, uint32_t value, int loop,
     absl::base_internal::SchedulingMode) {
-  if (loop != 0) {
-    int save_errno = errno;
-    struct timespec tm;
-    tm.tv_sec = 0;
-    // Increase the delay; we expect (but do not rely on) explicit wakeups.
-    // We don't rely on explicit wakeups because we intentionally allow for
-    // a race on the kSpinLockSleeper bit.
-    tm.tv_nsec = 16 * absl::base_internal::SpinLockSuggestedDelayNS(loop);
-    syscall(SYS_futex, w, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, value, &tm);
-    errno = save_errno;
-  }
+  int save_errno = errno;
+  struct timespec tm;
+  tm.tv_sec = 0;
+  tm.tv_nsec = absl::base_internal::SpinLockSuggestedDelayNS(loop);
+  syscall(SYS_futex, w, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, value, &tm);
+  errno = save_errno;
 }
 
 ABSL_ATTRIBUTE_WEAK void AbslInternalSpinLockWake(std::atomic<uint32_t> *w,
diff --git a/absl/base/internal/spinlock_wait.cc b/absl/base/internal/spinlock_wait.cc
index 365a7939494f..7e4f435245a7 100644
--- a/absl/base/internal/spinlock_wait.cc
+++ b/absl/base/internal/spinlock_wait.cc
@@ -65,17 +65,14 @@ int SpinLockSuggestedDelayNS(int loop) {
   r = 0x5deece66dLL * r + 0xb;   // numbers from nrand48()
   delay_rand.store(r, std::memory_order_relaxed);
 
-  r <<= 16;   // 48-bit random number now in top 48-bits.
   if (loop < 0 || loop > 32) {   // limit loop to 0..32
     loop = 32;
   }
-  // loop>>3 cannot exceed 4 because loop cannot exceed 32.
-  // Select top 20..24 bits of lower 48 bits,
-  // giving approximately 0ms to 16ms.
-  // Mean is exponential in loop for first 32 iterations, then 8ms.
-  // The futex path multiplies this by 16, since we expect explicit wakeups
-  // almost always on that path.
-  return static_cast<int>(r >> (44 - (loop >> 3)));
+  const int kMinDelay = 128 << 10;  // 128us
+  // Double delay every 8 iterations, up to 16x (2ms).
+  int delay = kMinDelay << (loop / 8);
+  // Randomize in delay..2*delay range, for resulting 128us..4ms range.
+  return delay | ((delay - 1) & static_cast<int>(r));
 }
 
 }  // namespace base_internal
diff --git a/absl/container/BUILD.bazel b/absl/container/BUILD.bazel
index 87fc7349618a..acdbc473d961 100644
--- a/absl/container/BUILD.bazel
+++ b/absl/container/BUILD.bazel
@@ -447,8 +447,20 @@ cc_library(
 )
 
 cc_library(
+    name = "hashtablez_force_sampling",
+    srcs = ["internal/hashtablez_force_sampling.cc"],
+    copts = ABSL_DEFAULT_COPTS,
+    deps = [
+        ":hashtablez_sampler",
+    ],
+)
+
+cc_library(
     name = "hashtablez_sampler",
-    srcs = ["internal/hashtablez_sampler.cc"],
+    srcs = [
+        "internal/hashtablez_sampler.cc",
+        "internal/hashtablez_sampler_force_weak_definition.cc",
+    ],
     hdrs = ["internal/hashtablez_sampler.h"],
     copts = ABSL_DEFAULT_COPTS,
     deps = [
@@ -476,6 +488,20 @@ cc_test(
     ],
 )
 
+cc_test(
+    name = "hashtablez_force_sampling_test",
+    srcs = ["internal/hashtablez_force_sampling_test.cc"],
+    tags = [
+        "no_test_darwin_x86_64",
+        "no_test_msvc_x64",
+    ],
+    deps = [
+        ":hashtablez_force_sampling",
+        ":hashtablez_sampler",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_library(
     name = "node_hash_policy",
     hdrs = ["internal/node_hash_policy.h"],
diff --git a/absl/container/CMakeLists.txt b/absl/container/CMakeLists.txt
index 21c9cb95cfda..822388bd5518 100644
--- a/absl/container/CMakeLists.txt
+++ b/absl/container/CMakeLists.txt
@@ -444,6 +444,7 @@ absl_cc_library(
     "internal/hashtablez_sampler.h"
   SRCS
     "internal/hashtablez_sampler.cc"
+    "internal/hashtablez_sampler_force_weak_definition.cc"
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
@@ -465,6 +466,30 @@ absl_cc_test(
 
 absl_cc_library(
   NAME
+    hashtablez_force_sampling
+  SRCS
+    "internal/hashtablez_force_sampling.cc"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  DEPS
+    absl::base
+    absl::have_sse
+    absl::synchronization
+)
+
+absl_cc_test(
+  NAME
+    hashtablez_force_sampling_test
+  SRCS
+    "internal/hashtablez_force_sampling_test.cc"
+  DEPS
+    absl::hashtablez_force_sampling
+    absl::hashtablez_sampler
+    gmock_main
+)
+
+absl_cc_library(
+  NAME
     hashtable_debug
   HDRS
     "internal/hashtable_debug.h"
diff --git a/absl/container/inlined_vector.h b/absl/container/inlined_vector.h
index 649e904a9704..6625d43f1745 100644
--- a/absl/container/inlined_vector.h
+++ b/absl/container/inlined_vector.h
@@ -82,10 +82,6 @@ class InlinedVector {
       std::forward_iterator_tag>;
 
   template <typename Iterator>
-  using DisableIfIntegral =
-      absl::enable_if_t<!std::is_integral<Iterator>::value>;
-
-  template <typename Iterator>
   using EnableIfAtLeastInputIterator =
       absl::enable_if_t<IsAtLeastInputIterator<Iterator>::value>;
 
@@ -152,7 +148,8 @@ class InlinedVector {
   // NOTE: The `enable_if` prevents ambiguous interpretation between a call to
   // this constructor with two integral arguments and a call to the above
   // `InlinedVector(size_type, const_reference)` constructor.
-  template <typename InputIterator, DisableIfIntegral<InputIterator>* = nullptr>
+  template <typename InputIterator,
+            EnableIfAtLeastInputIterator<InputIterator>* = nullptr>
   InlinedVector(InputIterator first, InputIterator last,
                 const allocator_type& alloc = allocator_type())
       : allocator_and_tag_(alloc) {
@@ -516,7 +513,8 @@ class InlinedVector {
 
   // Overload of `InlinedVector::assign()` to replace the contents of the
   // inlined vector with values constructed from the range [`first`, `last`).
-  template <typename InputIterator, DisableIfIntegral<InputIterator>* = nullptr>
+  template <typename InputIterator,
+            EnableIfAtLeastInputIterator<InputIterator>* = nullptr>
   void assign(InputIterator first, InputIterator last) {
     AssignRange(first, last);
   }
diff --git a/absl/container/internal/hashtablez_force_sampling.cc b/absl/container/internal/hashtablez_force_sampling.cc
new file mode 100644
index 000000000000..868976ec5240
--- /dev/null
+++ b/absl/container/internal/hashtablez_force_sampling.cc
@@ -0,0 +1,24 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/hashtablez_sampler.h"
+
+namespace absl {
+namespace container_internal {
+
+// See hashtablez_sampler.h for details.
+extern "C" const bool kAbslContainerInternalSampleEverything = true;
+
+}  // namespace container_internal
+}  // namespace absl
diff --git a/absl/container/internal/hashtablez_force_sampling_test.cc b/absl/container/internal/hashtablez_force_sampling_test.cc
new file mode 100644
index 000000000000..9ff1046a9ad3
--- /dev/null
+++ b/absl/container/internal/hashtablez_force_sampling_test.cc
@@ -0,0 +1,60 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstddef>
+
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/container/internal/hashtablez_sampler.h"
+
+namespace absl {
+namespace container_internal {
+
+class HashtablezInfoHandlePeer {
+ public:
+  static bool IsSampled(const HashtablezInfoHandle& h) {
+    return h.info_ != nullptr;
+  }
+};
+
+namespace {
+
+bool samples[3]{true, true, true};
+
+// We do this test in a global object to test that this works even before main.
+struct Global {
+  Global() {
+    // By default it is sampled.
+    samples[0] = HashtablezInfoHandlePeer::IsSampled(Sample());
+
+    // Even with a large parameter, it is sampled.
+    SetHashtablezSampleParameter(100);
+    samples[1] = HashtablezInfoHandlePeer::IsSampled(Sample());
+
+    // Even if we turn it off, it is still sampled.
+    SetHashtablezEnabled(false);
+    samples[2] = HashtablezInfoHandlePeer::IsSampled(Sample());
+  }
+} global;
+
+TEST(kAbslContainerInternalSampleEverything, Works) {
+  EXPECT_THAT(samples, testing::Each(true));
+  EXPECT_TRUE(kAbslContainerInternalSampleEverything);
+  // One more after main()
+  EXPECT_TRUE(HashtablezInfoHandlePeer::IsSampled(Sample()));
+}
+
+}  // namespace
+}  // namespace container_internal
+}  // namespace absl
diff --git a/absl/container/internal/hashtablez_sampler.cc b/absl/container/internal/hashtablez_sampler.cc
index 1ba9564513e2..7c411140be49 100644
--- a/absl/container/internal/hashtablez_sampler.cc
+++ b/absl/container/internal/hashtablez_sampler.cc
@@ -116,6 +116,11 @@ HashtablezSampler& HashtablezSampler::Global() {
   return *sampler;
 }
 
+HashtablezSampler::DisposeCallback HashtablezSampler::SetDisposeCallback(
+    DisposeCallback f) {
+  return dispose_.exchange(f, std::memory_order_relaxed);
+}
+
 HashtablezInfo::HashtablezInfo() { PrepareForSampling(); }
 HashtablezInfo::~HashtablezInfo() = default;
 
@@ -138,7 +143,7 @@ void HashtablezInfo::PrepareForSampling() {
 }
 
 HashtablezSampler::HashtablezSampler()
-    : dropped_samples_(0), size_estimate_(0), all_(nullptr) {
+    : dropped_samples_(0), size_estimate_(0), all_(nullptr), dispose_(nullptr) {
   absl::MutexLock l(&graveyard_.init_mu);
   graveyard_.dead = &graveyard_;
 }
@@ -161,6 +166,10 @@ void HashtablezSampler::PushNew(HashtablezInfo* sample) {
 }
 
 void HashtablezSampler::PushDead(HashtablezInfo* sample) {
+  if (auto* dispose = dispose_.load(std::memory_order_relaxed)) {
+    dispose(*sample);
+  }
+
   absl::MutexLock graveyard_lock(&graveyard_.init_mu);
   absl::MutexLock sample_lock(&sample->init_mu);
   sample->dead = graveyard_.dead;
@@ -220,6 +229,11 @@ int64_t HashtablezSampler::Iterate(
 }
 
 HashtablezInfo* SampleSlow(int64_t* next_sample) {
+  if (kAbslContainerInternalSampleEverything) {
+    *next_sample = 1;
+    return HashtablezSampler::Global().Register();
+  }
+
   bool first = *next_sample < 0;
   *next_sample = GetGeometricVariable(
       g_hashtablez_sample_parameter.load(std::memory_order_relaxed));
diff --git a/absl/container/internal/hashtablez_sampler.h b/absl/container/internal/hashtablez_sampler.h
index c42f1842ffe7..126a0ade431e 100644
--- a/absl/container/internal/hashtablez_sampler.h
+++ b/absl/container/internal/hashtablez_sampler.h
@@ -183,6 +183,13 @@ class HashtablezSampler {
   // Unregisters the sample.
   void Unregister(HashtablezInfo* sample);
 
+  // The dispose callback will be called on all samples the moment they are
+  // being unregistered. Only affects samples that are unregistered after the
+  // callback has been set.
+  // Returns the previous callback.
+  using DisposeCallback = void (*)(const HashtablezInfo&);
+  DisposeCallback SetDisposeCallback(DisposeCallback f);
+
   // Iterates over all the registered `StackInfo`s.  Returning the number of
   // samples that have been dropped.
   int64_t Iterate(const std::function<void(const HashtablezInfo& stack)>& f);
@@ -222,6 +229,8 @@ class HashtablezSampler {
   //
   std::atomic<HashtablezInfo*> all_;
   HashtablezInfo graveyard_;
+
+  std::atomic<DisposeCallback> dispose_;
 };
 
 // Enables or disables sampling for Swiss tables.
@@ -233,6 +242,13 @@ void SetHashtablezSampleParameter(int32_t rate);
 // Sets a soft max for the number of samples that will be kept.
 void SetHashtablezMaxSamples(int32_t max);
 
+// Configuration override.
+// This allows process-wide sampling without depending on order of
+// initialization of static storage duration objects.
+// The definition of this constant is weak, which allows us to inject a
+// different value for it at link time.
+extern "C" const bool kAbslContainerInternalSampleEverything;
+
 }  // namespace container_internal
 }  // namespace absl
 
diff --git a/absl/container/internal/hashtablez_sampler_force_weak_definition.cc b/absl/container/internal/hashtablez_sampler_force_weak_definition.cc
new file mode 100644
index 000000000000..38a3f2601c08
--- /dev/null
+++ b/absl/container/internal/hashtablez_sampler_force_weak_definition.cc
@@ -0,0 +1,27 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/container/internal/hashtablez_sampler.h"
+
+#include "absl/base/attributes.h"
+
+namespace absl {
+namespace container_internal {
+
+// See hashtablez_sampler.h for details.
+extern "C" ABSL_ATTRIBUTE_WEAK const bool
+    kAbslContainerInternalSampleEverything = false;
+
+}  // namespace container_internal
+}  // namespace absl
diff --git a/absl/container/internal/hashtablez_sampler_test.cc b/absl/container/internal/hashtablez_sampler_test.cc
index 31e7641a1222..f9ee941a015c 100644
--- a/absl/container/internal/hashtablez_sampler_test.cc
+++ b/absl/container/internal/hashtablez_sampler_test.cc
@@ -302,6 +302,31 @@ TEST(HashtablezSamplerTest, MultiThreaded) {
   stop.Notify();
 }
 
+TEST(HashtablezSamplerTest, Callback) {
+  HashtablezSampler sampler;
+
+  auto* info1 = Register(&sampler, 1);
+  auto* info2 = Register(&sampler, 2);
+
+  static const HashtablezInfo* expected;
+
+  auto callback = [](const HashtablezInfo& info) {
+    // We can't use `info` outside of this callback because the object will be
+    // disposed as soon as we return from here.
+    EXPECT_EQ(&info, expected);
+  };
+
+  // Set the callback.
+  EXPECT_EQ(sampler.SetDisposeCallback(callback), nullptr);
+  expected = info1;
+  sampler.Unregister(info1);
+
+  // Unset the callback.
+  EXPECT_EQ(callback, sampler.SetDisposeCallback(nullptr));
+  expected = nullptr;  // no more calls.
+  sampler.Unregister(info2);
+}
+
 }  // namespace
 }  // namespace container_internal
 }  // namespace absl
diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 8f6469fff7f3..8e3fa02d7e42 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -1035,7 +1035,7 @@ class raw_hash_set {
   size_t capacity() const { return capacity_; }
   size_t max_size() const { return (std::numeric_limits<size_t>::max)(); }
 
-  void clear() {
+  ABSL_ATTRIBUTE_REINITIALIZES void clear() {
     // Iterating over this container is O(bucket_count()). When bucket_count()
     // is much greater than size(), iteration becomes prohibitively expensive.
     // For clear() it is more important to reuse the allocated array when the
diff --git a/absl/time/clock.cc b/absl/time/clock.cc
index 74ee1401b98c..4863f643c2e0 100644
--- a/absl/time/clock.cc
+++ b/absl/time/clock.cc
@@ -379,7 +379,7 @@ static uint64_t UpdateLastSample(
 //
 // Manually mark this 'noinline' to minimize stack frame size of the fast
 // path.  Without this, sometimes a compiler may inline this big block of code
-// into the fast past.  That causes lots of register spills and reloads that
+// into the fast path.  That causes lots of register spills and reloads that
 // are unnecessary unless the slow path is taken.
 //
 // TODO(absl-team): Remove this attribute when our compiler is smart enough