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Even more thread-safety changes #49558
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Your PR failed on Travis. Through arcane magic we have determined that the following fragments from the build log may contain information about the problem. Click to expand the log.
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Ping from triage, @michaelwoerister ! |
☔ The latest upstream changes (presumably #49714) made this pull request unmergeable. Please resolve the merge conflicts. |
src/librustc_data_structures/sync.rs
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@@ -241,6 +242,75 @@ impl<K: Eq + Hash, V: Eq, S: BuildHasher> HashMapExt<K, V> for HashMap<K, V, S> | |||
} | |||
} | |||
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/// A type whose inner value can be written once and then will stay read-only | |||
pub struct Once<T>(Lock<Option<T>>, PhantomData<T>); |
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What's the PhantomData
for?
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Once
conceptually owns a T
outside the lock once it is initialized. This ensures we get the right impl for Sync
: impl<T: Sync> Sync for Once<T>
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Good catch! Could you add a comment explaining that?
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Plus maybe an example of how one could exploit Once<T>
if the PhantomData
was not there?
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Done.
@@ -154,13 +154,13 @@ fn get_llvm_opt_size(optimize: config::OptLevel) -> llvm::CodeGenOptSize { | |||
} | |||
} | |||
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pub fn create_target_machine(sess: &Session) -> TargetMachineRef { | |||
target_machine_factory(sess)().unwrap_or_else(|err| { | |||
pub fn create_target_machine(sess: &Session, find_features: bool) -> TargetMachineRef { |
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What's the find_features
parameter about?
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create_target_machine
calls is_pie_binary
which requires crate_types
. However when we are discovering the target CPU features, crate_types
is uninitialized. So we pass in find_features
to let create_target_machine
assume that we aren't looking at a pie binary.
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Ah, OK. Could you add a comment explaining that?
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Done.
src/librustc/traits/select.rs
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// This may overwrite the cache with the same value | ||
self.tcx().evaluation_cache | ||
.hashmap.borrow_mut() | ||
.insert(trait_ref, WithDepNode::new(dep_node, result)); |
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Should this use insert_same()
?
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The type inserted doesn't implement Eq
, so it cannot use insert_same
.
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For this one, implementing Eq
should be easy. Let's do it.
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Done.
src/librustc/traits/select.rs
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// This may overwrite the cache with the same value | ||
tcx.selection_cache | ||
.hashmap.borrow_mut() | ||
.insert(trait_ref, WithDepNode::new(dep_node, candidate)); |
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This might also be a candidate for insert_same()
.
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Same thing, the type inserted doesn't implement Eq
, so it cannot use insert_same
.
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Yeah, this one looks more complicated. Pity.
src/librustc_data_structures/sync.rs
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} | ||
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#[inline] | ||
pub fn try_set(&self, value: T) -> Option<T> { |
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Could you document this method, especially what the return value is.
src/librustc_data_structures/sync.rs
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} | ||
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#[inline(always)] | ||
pub fn try_get(&self) -> Option<&T> { |
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This method could use documentation too.
src/librustc_data_structures/sync.rs
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} | ||
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#[inline] | ||
pub fn init_locking<F: FnOnce() -> T>(&self, f: F) { |
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init_locking
and init_nonlocking
should be documented to. I needed a while to see what these are about but the difference can be explained rather quickly.
Looks great, thanks @Zoxc! |
@bors r+ |
📌 Commit 006f9b2 has been approved by |
Even more thread-safety changes r? @michaelwoerister
☀️ Test successful - status-appveyor, status-travis |
Make SelectionCache and EvaluationCache thread-safe Split out from #49558 r? @nikomatsakis
The included measurements have varied over the years. At one point there were quite a few more, but rust-lang#49558 deleted a lot that were no longer used. Today there's just four, and it's a motley collection that doesn't seem particularly valuable. I think it has been well and truly subsumed by self-profiling, which collects way more data.
The included measurements have varied over the years. At one point there were quite a few more, but rust-lang#49558 deleted a lot that were no longer used. Today there's just four, and it's a motley collection that doesn't seem particularly valuable. I think it has been well and truly subsumed by self-profiling, which collects way more data.
…wiser Remove `-Zperf-stats`. The included measurements have varied over the years. At one point there were quite a few more, but rust-lang#49558 deleted a lot that were no longer used. Today there's just four, and it's a motley collection that doesn't seem particularly valuable. I think it has been well and truly subsumed by self-profiling, which collects way more data. r? `@wesleywiser`
r? @michaelwoerister