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Make drv hash modulo memo table thread-safe

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Let's get one step closer to the daemon not needing to fork.
This commit is contained in:
John Ericson 2020-11-19 16:50:06 +00:00
parent 79aa7d9518
commit 2113ae2d85
3 changed files with 21 additions and 16 deletions
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7
src/libexpr/primops.cc
View file

@ -1132,9 +1132,10 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
However, we don't bother doing this for floating CA derivations because
their "hash modulo" is indeterminate until built. */
if (drv.type() != DerivationType::CAFloating)
drvHashes.insert_or_assign(drvPath,
hashDerivationModulo(*state.store, Derivation(drv), false));
if (drv.type() != DerivationType::CAFloating) {
auto h = hashDerivationModulo(*state.store, Derivation(drv), false);
drvHashes.lock()->insert_or_assign(drvPath, h);
}
state.mkAttrs(v, 1 + drv.outputs.size());
mkString(*state.allocAttr(v, state.sDrvPath), drvPathS, {"=" + drvPathS});

25
src/libstore/derivations.cc
View file

@ -451,7 +451,7 @@ DerivationType BasicDerivation::type() const
}
DrvHashes drvHashes;
Sync<DrvHashes> drvHashes;
/* pathDerivationModulo and hashDerivationModulo are mutually recursive
*/
@ -459,19 +459,22 @@ DrvHashes drvHashes;
/* Look up the derivation by value and memoize the
`hashDerivationModulo` call.
*/
static const DrvHashModulo & pathDerivationModulo(Store & store, const StorePath & drvPath)
static const DrvHashModulo pathDerivationModulo(Store & store, const StorePath & drvPath)
{
auto h = drvHashes.find(drvPath);
if (h == drvHashes.end()) {
// Cache it
h = drvHashes.insert_or_assign(
drvPath,
hashDerivationModulo(
{
auto hashes = drvHashes.lock();
auto h = hashes->find(drvPath);
if (h != hashes->end()) {
return h->second;
}
}
auto h = hashDerivationModulo(
store,
store.readInvalidDerivation(drvPath),
false)).first;
}
return h->second;
false);
// Cache it
drvHashes.lock()->insert_or_assign(drvPath, h);
return h;
}
/* See the header for interface details. These are the implementation details.

3
src/libstore/derivations.hh
View file

@ -210,7 +210,8 @@ DrvHashModulo hashDerivationModulo(Store & store, const Derivation & drv, bool m
/* Memoisation of hashDerivationModulo(). */
typedef std::map<StorePath, DrvHashModulo> DrvHashes;
extern DrvHashes drvHashes; // FIXME: global, not thread-safe
// FIXME: global, though at least thread-safe.
extern Sync<DrvHashes> drvHashes;
/* Memoisation of `readDerivation(..).resove()`. */
typedef std::map<