weaselab/versioned-map
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Fix two node-copying bugs in update

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This commit is contained in:
Andrew Noyes
2024-05-14 17:44:01 -07:00
parent 862fc3297c
commit 67c8ca8f3a
4 changed files with 74 additions and 17 deletions
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1
Facade.h
View File

@@ -136,7 +136,6 @@ struct Facade {
int64_t getVersion() const { return versioned.getVersion(); }
int64_t getOldestVersion() const { return versioned.getOldestVersion(); }
private:
std::vector<std::pair<String, String>> unversionedRead(const String &begin,
const String &end,
int &limit,

35
FacadeTest.cpp
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@@ -1,4 +1,5 @@
#include "Facade.h"
#include "PrintMutation.h"
#include "VersionedMap.h"
#include <inttypes.h>
@@ -24,6 +25,8 @@ weaselab::VersionedMap::Mutation clear(weaselab::VersionedMap::Key begin,
return {begin.p, end.p, begin.len, end.len, weaselab::VersionedMap::Clear};
}
void breakpoint_me() {}
int main() {
Facade f(0);
int64_t version = 1;
@@ -42,13 +45,14 @@ int main() {
}
for (int64_t i = 0; i < version; ++i) {
printf("--- version %" PRId64 " ---\n", i);
auto result = f.viewAt(i).rangeRead("a"_s, "d"_s, 10, false);
printf("merged:\n");
auto result = f.viewAt(i).rangeRead("a"_s, "z"_s, 100, false);
for (const auto &[k, v] : result) {
for (auto c : k) {
if (isprint(c)) {
printf("%c", c);
} else {
printf("0x%02x", c);
printf("x%02x", c);
}
}
printf(" -> ");
@@ -56,10 +60,35 @@ int main() {
if (isprint(c)) {
printf("%c", c);
} else {
printf("0x%02x", c);
printf("x%02x", c);
}
}
printf("\n");
}
printf("unversioned:\n");
for (const auto &[k, v] : f.unversioned) {
for (auto c : k) {
if (isprint(c)) {
printf("%c", c);
} else {
printf("x%02x", c);
}
}
printf(" -> ");
for (auto c : v) {
if (isprint(c)) {
printf("%c", c);
} else {
printf("x%02x", c);
}
}
printf("\n");
}
breakpoint_me();
printf("versioned:\n");
for (auto iter = f.versioned.begin(i), end = f.versioned.end(i);
iter != end; ++iter) {
printMutation(*iter);
}
}
}

29
PrintMutation.h
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@@ -1,6 +1,7 @@
#pragma once
#include "VersionedMap.h"
#include <ctype.h>
#include <inttypes.h>
#include <stdio.h>
@@ -10,22 +11,42 @@ printMutation(const weaselab::VersionedMap::Iterator::VersionedMutation &m) {
case weaselab::VersionedMap::Set:
printf("set ");
for (int i = 0; i < m.param1Len; ++i) {
printf("x%02x", m.param1[i]);
auto c = m.param1[i];
if (isprint(c)) {
printf("%c", c);
} else {
printf("x%02x", c);
}
}
printf(" -> '");
for (int i = 0; i < m.param2Len; ++i) {
printf("x%02x", m.param2[i]);
auto c = m.param2[i];
if (isprint(c)) {
printf("%c", c);
} else {
printf("x%02x", c);
}
}
printf("' @ %" PRId64 "\n", m.version);
break;
case weaselab::VersionedMap::Clear:
printf("clear [");
for (int i = 0; i < m.param1Len; ++i) {
printf("x%02x", m.param1[i]);
auto c = m.param1[i];
if (isprint(c)) {
printf("%c", c);
} else {
printf("x%02x", c);
}
}
printf(", ");
for (int i = 0; i < m.param2Len; ++i) {
printf("x%02x", m.param2[i]);
auto c = m.param2[i];
if (isprint(c)) {
printf("%c", c);
} else {
printf("x%02x", c);
}
}
printf(") @ %" PRId64 "\n", m.version);
break;

26
VersionedMap.cpp
View File

@@ -638,7 +638,8 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
auto &c = mm.base[copy];
c.entry = n.entry->addref();
c.pointer[which] = child;
c.pointer[!which] = n.pointer[!which];
c.pointer[!which] =
this->child<std::memory_order_relaxed>(node, !which, latestVersion);
c.updated.store(false, std::memory_order_relaxed);
c.updateVersion = version;
assert(copy == 0 || copy >= kMinAddressable);
@@ -649,11 +650,12 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
// The reason these aren't data races is that concurrent readers are
// reading < `version`
if (updated && n.replacedPointer != which) {
auto result = doCopy();
// We can't update n.replacedPointer without introducing a data race
// (unless we packed it into the atomic?) so we copy. pointer[2] becomes
// unreachable, but need to tell the garbage collector.
n.pointer[2] = 0;
return doCopy();
return result;
} else if (updated) {
n.pointer[2] = child;
} else {
@@ -808,12 +810,13 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
void remove(Finger &finger) {
#ifndef NDEBUG
uint32_t expected;
Entry *expected;
{
Finger copy;
finger.copyTo(copy);
move<std::memory_order_relaxed>(copy, latestVersion, true);
expected = copy.searchPathSize() > 0 ? copy.backNode() : 0;
expected =
copy.searchPathSize() > 0 ? mm.base[copy.backNode()].entry : nullptr;
}
#endif
@@ -850,7 +853,7 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
// propagate up the search path, all the way to the root since we may have
// more rotations to do even if an update doesn't change a node pointer
auto node = finger.backNode();
const auto oldSize = finger.searchPathSize();
const auto oldSize = finger.searchPathSize() - (node == 0);
for (;;) {
if (finger.searchPathSize() == 1) {
// Made it to the root
@@ -873,12 +876,17 @@ struct __attribute__((__visibility__("hidden"))) VersionedMap::Impl {
finger.push(c, false);
}
} else {
move<std::memory_order_relaxed>(finger, latestVersion, true);
while (finger.searchPathSize() > 1 && finger.backDirection() == true) {
finger.pop();
}
finger.pop();
}
#ifndef NDEBUG
if (finger.searchPathSize() > 0) {
assert(finger.backNode() == expected);
assert(mm.base[finger.backNode()].entry == expected);
} else {
assert(expected == nullptr);
}
#endif
}
@@ -1342,7 +1350,7 @@ void VersionedMap::Impl::printInOrderHelper(int64_t version, uint32_t node,
return;
}
printInOrderHelper(version,
child<std::memory_order_relaxed>(node, false, version),
child<std::memory_order_relaxed>(node, true, version),
depth + 1);
for (int i = 0; i < depth; ++i) {
printf(" ");
@@ -1360,7 +1368,7 @@ void VersionedMap::Impl::printInOrderHelper(int64_t version, uint32_t node,
}
printf("\n");
VersionedMap::Impl::printInOrderHelper(
version, child<std::memory_order_relaxed>(node, true, version),
version, child<std::memory_order_relaxed>(node, false, version),
depth + 1);
}