diff options
Diffstat (limited to 'compiler/codeGen')
| -rw-r--r-- | compiler/codeGen/StgCmmClosure.hs | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/compiler/codeGen/StgCmmClosure.hs b/compiler/codeGen/StgCmmClosure.hs index 850632c3b1..f8741b7fb6 100644 --- a/compiler/codeGen/StgCmmClosure.hs +++ b/compiler/codeGen/StgCmmClosure.hs @@ -778,12 +778,12 @@ Note [Black-holing non-updatable thunks] ========================================= We cannot black-hole non-updatable thunks otherwise we run into issues like -#10414. A single-entry (non-updatable) thunk can actually be entered more than -once in a parallel program, if work is duplicated by two threads both entering -the same updatable thunk before the other has blackholed it. So, we must not -eagerly blackhole non-updatable thunks, or the second thread to enter one will -become blocked indefinitely. (They are not blackholed by lazy blackholing -either, since they have no associated update frame.) +Trac #10414. A single-entry (non-updatable) thunk can actually be entered more +than once in a parallel program, if work is duplicated by two threads both +entering the same updatable thunk before the other has blackholed it. So, we +must not eagerly blackhole non-updatable thunks, or the second thread to enter +one will become blocked indefinitely. (They are not blackholed by lazy +blackholing either, since they have no associated update frame.) For instance, let's consider the following value (in pseudo-Core, example due to Reid Barton), |