Matt Arant
d058322cc6
Every crash root-caused earlier tonight (Subscription::subscribers, TCPServer::sessions, the Socket::write()/eventReceived() re-arm race) was the same underlying shape: some thread calling a method - or Thread::run() calling delete - on a TCPSession* while another thread concurrently freed that same object, because nothing actually guaranteed the object stayed alive for the duration of a call. Mutex-based patches at each individual call site kept narrowing the window without closing it (confirmed live, repeatedly, via AddressSanitizer under concurrent load - each fix produced a new, different crash signature at the same underlying race), and adding more locks around every write() call also works against the fifo-based design's own goal: no thread should have to block just to hand a message to another thread's session. TCPSession now derives from std::enable_shared_from_this<TCPSession> and exposes pin() - a safe upgrade from a stored raw pointer to a real, ownership-extending shared_ptr, returning nullptr instead of throwing once the object's real owner has let go. TCPServer::sessions is now the one real strong-owning shared_ptr<TCPSession> per live session; every other place that stores a TCPSession* (Subscription::subscribers, Zephora's own sessionsByPlayerName, GroupObject's membership list, etc.) is just a non-owning observer and must pin() before touching the object. A second, distinct problem: Thread::run()'s epoll dispatch starts from a raw void* of unknown validity. An early version of this fix used dynamic_cast<TCPSession*> to identify session objects before calling pin() - confirmed live via AddressSanitizer that dynamic_cast itself segfaults on a stale pointer, since it has to read the (potentially freed) object's own vtable to work at all. TCPSession::tryGet()/TCPServer:: isKnownListeningSocket() replace that: both look the raw pointer up as a key in a registry, never dereferencing it for the check itself - safe to call on any value, live session, immortal listening socket, or fully freed garbage alike. Verified via an AddressSanitizer-instrumented build under sustained concurrent load (up to 15-way parallel connect/subscribe/create/disconnect cycles, multiple rounds, 100+ total connections) with zero errors, then against the real production build with a genuine 500-connection load test (463/500 succeeded; the rest hit the process's own file-descriptor ulimit under peak burst, an unrelated and separately deferred tuning matter, not a crash). Files touched: TCPSession.h (enable_shared_from_this, pin(), the tryGet() registry), TCPServer.h/.cpp (sessions as shared_ptr, isKnownListening Socket() registry, lock made protected for subclasses), Thread.cpp (the whole dispatch rewrite), Subscription.cpp/SubscriptionManager.cpp (every subscriber write() site now pin()s first), ConsoleServer.cpp (logSend() was iterating `sessions` with no lock at all - fixed alongside the type change it needed anyway).
76 lines
1.8 KiB
C++
76 lines
1.8 KiB
C++
#include "Timer.h"
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#include <sys/timerfd.h>
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#include <math.h>
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namespace core
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{
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Timer::Timer(EPoll &ePoll, double delay = 0.0f) : Socket(ePoll, "Timer")
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{
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// See preventSelfDelete's own doc comment on Socket - a Timer is
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// always a subobject of some larger composite (e.g. ZephoraSession
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// : TCPSession, Timer), never a standalone connection, so its own
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// eventReceived() must never be allowed to signal "delete me" to
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// Thread::run()'s generic dispatch.
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preventSelfDelete = true;
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setDescriptor(timerfd_create(CLOCK_REALTIME, 0));
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setTimer(delay);
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}
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Timer::~Timer()
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{
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}
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void Timer::setTimer(double delay)
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{
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double integer;
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double fraction;
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struct itimerspec timer;
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delayValue = delay;
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timer.it_interval.tv_sec = 0;
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timer.it_interval.tv_nsec = 0;
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fraction = modf(delay, &integer);
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timer.it_value.tv_sec = (int)integer;
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timer.it_value.tv_nsec = (int)(fraction * 1000000000);
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timerfd_settime(getDescriptor(), 0, &timer, NULL);
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}
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void Timer::clearTimer()
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{
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struct itimerspec timer;
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timer.it_interval.tv_sec = 0;
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timer.it_interval.tv_nsec = 0;
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timer.it_value.tv_sec = 0;
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timer.it_value.tv_nsec = 0;
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timerfd_settime(getDescriptor(), 0, &timer, NULL);
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}
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double Timer::getElapsed()
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{
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struct itimerspec timer;
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timerfd_gettime(getDescriptor(), &timer);
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double toTimeout = (double)((timer.it_value.tv_sec * 1000000000L) + timer.it_value.tv_nsec) / 1000000000L;
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return delayValue - toTimeout;
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}
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void Timer::onDataReceived(std::string data)
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{
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onTimeout();
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}
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double Timer::getEpoch()
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{
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return (double)std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::system_clock::now().time_since_epoch()).count() / 1000000000L;
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}
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}
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