Subject: [boost] [interprocess] interprocess_condition blocks on notify_all if other process crashes
From: Remi Chateauneu (remi.chateauneu_at_[hidden])
Date: 2016-10-20 19:27:51
When two processes share memory, and if one of them dies leaving a mutex
in locked state, then the other process blocks on a notify using a
interprocess_condition, stored in shared memory.
This is described here:
The reason is that this condition uses in general, a
ipcdetail::spin_condition. Here is what it does in
inline void spin_condition::notify(boost::uint32_t command)
//This mutex guarantees that no other thread can enter to the
//do_timed_wait method logic, so that thread count will be
//constant until the function writes a NOTIFY_ALL command.
//It also guarantees that no other notification can be signaled
//on this spin_condition before this one ends
It locks an internal mutex, and if it is already locked and not unlocked
by the crashed process, we are blocked.
A fix is to replace lock() by:
if( ! m_enter_mut.timed_lock(delay) )
A cleaner fix would be to derive a subclass from spin_condition to
implement something like:
bool derived_spin_condition::timed_notify(boost::uint32_t, ptime delay)
What do you think ? Thanks.
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