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std::thread throws std::system_error when pthread_create is refused
(RLIMIT_NPROC, a container's pids cgroup, memory pressure), and nothing
caught it, so the node died by std::terminate. Threads are spawned per
peer connection, so the pressure that triggers this scales with peer
count, which is attacker-influenced. Observed killing a healthy
participant worker mid-mining.
Every spawn site in the node build, and what a failure now does:
- btftunnel.cpp: both tunnel pumps are guarded. The inbound pump starts
first because it owns cleanup of the pump end and rendezvous socket;
if the second spawn is refused, shutdown() wakes the first out of its
read and it cleans up itself -- closing those descriptors from the
failure path instead would race it onto reused descriptors. Both
paths return INVALID_SOCKET, which every caller already treats as
"this connection failed".
- btfrv.cpp: the relay's accept loop drops the connection it cannot
serve and stops accepting for a moment -- longer after consecutive
failures, capped at 5s -- instead of dying at an arbitrary one. The
per-pair second pump now runs on the handling thread itself, leaving
exactly one spawn to guard and nothing running yet to race.
- main.cpp: a participant that cannot spawn its hash workers stops the
ones that did start, drops the pool connection, and returns to the
reconnect loop, the same way an ordinary disconnect does.
- randomx_pow.cpp: dataset init joins the workers it got, releases the
dataset, and stays in light mode -- the same trade the allocation
failure path above it already makes.
- rpc.cpp, net.cpp: the remaining unchecked _beginthread calls (which
report failure by value, they cannot throw) now say precisely what
did not start. The pool's accept and payout threads failing silently
left the pool running deaf -- nobody accepts, nobody gets paid, and
nothing in the log says why.
Left alone deliberately: the per-relay accept spawns (rpc.cpp) already
check, log and retry on the next poll; startup-critical spawns in
net.cpp keep failing hard; the selftest-only std::thread uses may abort
a selftest run, which is acceptable where dying over one peer is not.
Verified: full node rebuilds clean and links; pool-stratum selftest
passes; a scratch harness under RLIMIT_NPROC=1 confirms _beginthread
reports -1 and std::thread throws system_error, the premises of every
path above.
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Every miner thread calls RandomXInitDataset at startup. Its only guard is
g_fFast, which is set at the very end -- after the ~2 GB dataset has been
filled, which takes tens of seconds. So all of them sailed past the guard
together and each allocated its own dataset.
Measured in production on a 32-core machine running 31 miner threads: the
log says "initializing ~2 GB dataset" 34 times, and the process holds
65,127 MB of private pages while its own startup line promises 2142 MB
"(~2080 MB shared RandomX dataset + ~2 MB per thread)". The word shared
was not true. A 4-core machine showed the same thing at its own scale: 4
allocations for 3 threads.
The waste was the mild half. g_dataset is assigned the moment memory is
allocated, before it holds anything, so the last thread to allocate swung
the pointer out from under threads still filling their own. A miner could
then hash against a dataset another thread had not finished writing, and
proof of work computed that way is not reproducible by any other node --
the block would be found invalid by everyone, including this node's own
verifier, which uses the cache rather than the dataset.
This only became reachable with multi-threaded mining (#52); with one
thread there was nobody to race.
Holding the lock across the whole initialisation is deliberate: a thread
arriving mid-init has nothing useful to do until the dataset exists, and
blocking is how it waits for exactly that.
Verified with three mining threads: one "initializing ~2 GB dataset", one
"dataset ready", and 2362 MB of private memory against 2086 MB advertised
-- the difference being the 256 MB cache. Before, three threads meant three
datasets.
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Satoshi's bitcoin-0.1.0 reborn with RandomX CPU proof of work, anonymous .btf
addressing over Nostr with CGNAT rendezvous, automatic peer discovery, a
headless Linux node, and Windows GUI wallet. Fair launch, no premine, 21M cap.
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