diff options
Diffstat (limited to 'manual')
| -rw-r--r-- | manual/src/cmds/intf-c.etex | 1 | ||||
| -rw-r--r-- | manual/src/tutorials/parallelism.etex | 10 |
2 files changed, 11 insertions, 0 deletions
diff --git a/manual/src/cmds/intf-c.etex b/manual/src/cmds/intf-c.etex index d1473fcf09..fcdaf2453c 100644 --- a/manual/src/cmds/intf-c.etex +++ b/manual/src/cmds/intf-c.etex @@ -2433,6 +2433,7 @@ When OCaml calls the C code implementing a primitive, the domain lock is held, therefore the C code has full access to the facilities of the run-time system. However, no other thread in the same domain can execute OCaml code concurrently with the C code of the primitive. +See also chapter~\ref{s:par_c_bindings} for the behaviour with multiple domains. If a C primitive runs for a long time or performs potentially blocking input-output operations, it can explicitly release the domain lock, diff --git a/manual/src/tutorials/parallelism.etex b/manual/src/tutorials/parallelism.etex index 127335b8ab..1d41cb9035 100644 --- a/manual/src/tutorials/parallelism.etex +++ b/manual/src/tutorials/parallelism.etex @@ -594,6 +594,16 @@ systhread identifiers uniquely identify systhreads in the program. The initial domain gets the domain id and the thread id as 0. The newly spawned domain gets domain id as 1. +\section{s:par_c_bindings}{Interaction with C bindings} + +During parallel execution with multiple domains, C code running on a domain may +run in parallel with any C code running in other domains even if neither of +them has released the ``domain lock''. Prior to OCaml 5.0, C bindings may have +assumed that if the OCaml runtime lock is not released, then it would be safe +to manipulate global C state (e.g. initialise a function-local static value). +This is no longer true in the presence of parallel execution with multiple +domains. + \section{s:par_atomics}{Atomics} Mutex, condition variables and semaphores are used to implement blocking |