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\section simgrid_dev_guide_simcall How to add a new simcall?
-A simcall is used to go from user mode to kernel mode. The workflow of
-a simcall is the following:
+
+A simcall is used to go from user mode to kernel mode. There is some
+sort of popping dance involved, as we want to isolate the user
+contextes from their environment (so that they can run in parallel).
+
+The workflow of a simcall is the following:
- `<ret> simcall_<name>(<args>)`
- `simcall_BODY_<name>(<args>)`
- - create the simcall
- - `SIMIX_process_yield` if not maestro
+ - Initializes the simcall (store the arguments in position)
+ - If maestro, executes the simcall directly (and return)
+ - If not, call `SIMIX_process_yield` to give back the control to maestro
- ========== KERNEL MODE ==========
- - `SIMIX_simcall_enter`
- - `SIMIX_pre_<name>(simcall, <args>)`
- - `SIMIX_simcall_answer(simcall)`
-
-To simplify the simcall creation, we have made a python script that
-generate most of the code and give helpers for the remaining stuff.
-That script reads the simcall definitions from src/simix/simcalls.in
-and generates the following files:
+ - `SIMIX_simcall_handle` large switch (on simcall) doing for each:
+ - `simcall_HANDLER_<name>(simcall, <args>)` (the manual code handling the simcall)
+ - If the simcall is not marked as "blocking" in its definition,
+ call `SIMIX_simcall_answer(simcall)` that adds back the issuer
+ process to the list of processes to run in the next scheduling round.
+ It is thus the responsability of the blocking simcalls to call
+ `SIMIX_simcall_answer(simcall)` themselves in their handler.
+
+Note that empty HANDLERs can be omitted. These functions usually do
+some parameter checking, or retrieve some information about the
+simcall issuer, but when there no need for such things, the handler
+can be omited. In that case, we directly call the function
+`simcall_<name>(<args>)`.
+
+To simplify the simcall creation, a python script generates most of
+the code and give helpers for the remaining stuff. That script reads
+the simcall definitions from src/simix/simcalls.in, checks that both
+`simcall_<name>()` and `simcall_HANDLER()` are defined somewhere, and
+generates the following files:
- smx_popping_accessors.h:
Helper functions to get and set simcall arguments and results
Definitions of `simcall_names[]` (debug name of each simcall), and
SIMIX_simcall_enter() that deals with the simcall from within the kernel
-Furthermode if the simcall_<name> or the SIMIX_pre_<name> function are missing,
-a warning will show up with a prototype of the corresponding fonction to fill.
-
The simcall.in file list all the simcalls in sections. A line starting by "##"
define a new section which will be replace by a "ifdef" in the generated code.
There is a simcall by line which follow this format:
