diff options
| author | Gabor Greif <ggreif@gmail.com> | 2020-01-22 18:24:14 -0500 |
|---|---|---|
| committer | Gabor Greif <ggreif@gmail.com> | 2020-01-22 18:24:14 -0500 |
| commit | ef56347debb950afc9452391f98c099d0b17ef56 (patch) | |
| tree | e3321d50e90a6471875e7f6cdd62f9da1ded0ef3 | |
| parent | 3dae006fc424e768bb43fc73851a08fefcb732a5 (diff) | |
| download | haskell-wip/ggreif-openFileBlocking.tar.gz | |
Document the fact, that openFileBlocking can consume an OS thread indefinitely.wip/ggreif-openFileBlocking
Also state that a deadlock can happen with the non-threaded runtime.
[ci skip]
| -rw-r--r-- | libraries/base/GHC/IO/Handle/FD.hs | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/libraries/base/GHC/IO/Handle/FD.hs b/libraries/base/GHC/IO/Handle/FD.hs index 64179768c9..122331f17d 100644 --- a/libraries/base/GHC/IO/Handle/FD.hs +++ b/libraries/base/GHC/IO/Handle/FD.hs @@ -150,6 +150,11 @@ openFile fp im = -- This can be useful for opening a FIFO for writing: if we open in -- non-blocking mode then the open will fail if there are no readers, -- whereas a blocking open will block until a reader appear. +-- +-- Note: when blocking happens, an OS thread becomes tied up with the +-- processing, so the program must have at least another OS thread if +-- it wants to unblock itself. By corollary, a non-threaded runtime +-- will need a process-external trigger in order to become unblocked. -- -- @since 4.4.0.0 openFileBlocking :: FilePath -> IOMode -> IO Handle |