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DRTVWR-476: Fix LLCoprocedurePool::enqueueCoprocedure() shutdown crash.

master
Nat Goodspeed 2020-05-20 10:44:34 -04:00
parent a07553c224
commit b7d60f650d
1 changed files with 33 additions and 10 deletions
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43
indra/llmessage/llcoproceduremanager.cpp
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@ -325,16 +325,22 @@ LLUUID LLCoprocedurePool::enqueueCoprocedure(const std::string &name, LLCoproced
LL_INFOS("CoProcMgr") << "Coprocedure(" << name << ") enqueuing with id=" << id.asString() << " in pool \"" << mPoolName << "\" at " << mPending << LL_ENDL;
auto pushed = mPendingCoprocs->try_push(boost::make_shared<QueuedCoproc>(name, id, proc));
// We don't really have a lot of good options if try_push() failed,
// perhaps because the consuming coroutine is gummed up or something. This
// method is probably called from code called by mainloop. If we toss an
// llcoro::suspend() call here, we'll circle back for another mainloop
// iteration, possibly resulting in being re-entered here. Let's avoid that.
LL_ERRS_IF(pushed != boost::fibers::channel_op_status::success, "CoProcMgr")
<< "Enqueue failed because queue is " << int(pushed) << LL_ENDL;
++mPending;
if (pushed == boost::fibers::channel_op_status::success)
{
++mPending;
return id;
}
return id;
// Here we didn't succeed in pushing. Shutdown could be the reason.
if (pushed == boost::fibers::channel_op_status::closed)
{
LL_WARNS("CoProcMgr") << "Discarding coprocedure '" << name << "' because shutdown" << LL_ENDL;
return {};
}
// The queue should never fill up.
LL_ERRS("CoProcMgr") << "Enqueue failed (" << unsigned(pushed) << ")" << LL_ENDL;
return {}; // never executed, pacify the compiler
}
//-------------------------------------------------------------------------
@ -344,6 +350,23 @@ void LLCoprocedurePool::coprocedureInvokerCoro(
{
for (;;)
{
// It is VERY IMPORTANT that we instantiate a new ptr_t just before
// the pop_wait_for() call below. When this ptr_t was declared at
// function scope (outside the for loop), NickyD correctly diagnosed a
// mysterious hang condition due to:
// - the second time through the loop, the ptr_t held the last pointer
// to the previous QueuedCoproc, which indirectly held the last
// LLPointer to an LLInventoryCallback instance
// - while holding the lock on pendingCoprocs, pop_wait_for() assigned
// the popped value to the ptr_t variable
// - assignment destroyed the previous value of that variable, which
// indirectly destroyed the LLInventoryCallback
// - whose destructor called ~LLRequestServerAppearanceUpdateOnDestroy()
// - which called LLAppearanceMgr::requestServerAppearanceUpdate()
// - which called enqueueCoprocedure()
// - which tried to acquire the lock on pendingCoprocs... alas.
// Using a fresh, clean ptr_t ensures that no previous value is
// destroyed during pop_wait_for().
QueuedCoproc::ptr_t coproc;
boost::fibers::channel_op_status status;
{
@ -357,7 +380,7 @@ void LLCoprocedurePool::coprocedureInvokerCoro(
if(status == boost::fibers::channel_op_status::timeout)
{
LL_INFOS_ONCE() << "pool '" << mPoolName << "' stalled." << LL_ENDL;
LL_DEBUGS_ONCE("CoProcMgr") << "pool '" << mPoolName << "' waiting." << LL_ENDL;
continue;
}
// we actually popped an item