[PATCH amend 08/14] Add infrastructure to run a function asynchronously.
- From
Johannes Sixt <johannes.sixt@telecom.at>
- Date
- Oct 14, 2007, 17:08 UTC
- Message-ID
- <200710141908.45779.johannes.sixt@telecom.at>
- In-Reply-To
- <1192305984-22594-9-git-send-email-johannes.sixt@telecom.at>
This adds start_async() and finish_async(), which runs a function asynchronously. Communication with the caller happens only via pipes. For this reason, this implementation forks off a child process that runs the function.
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at> ---
This is the same as submitted previously except it uses close_pair() to close the pipe in an error patch and improves the comments in run-command.h.
-- Hannes
run-command.c | 52 ++++++++++++++++++++++++++++++++++++++++++++-------- run-command.h | 22 ++++++++++++++++++++++ 2 files changed, 66 insertions(+), 8 deletions(-)
diff --git a/run-command.c b/run-command.c index d00c03b..db02f75 100644 --- a/run-command.c +++ b/run-command.c @@ -127,16 +127,11 @@ int start_command(struct child_process *cmd) return 0; } -int finish_command(struct child_process *cmd) +static int wait_or_whine(pid_t pid) { - if (cmd->close_in) - close(cmd->in); - if (cmd->close_out) - close(cmd->out); - for (;;) { int status, code; - pid_t waiting = waitpid(cmd->pid, &status, 0); + pid_t waiting = waitpid(pid, &status, 0); if (waiting < 0) { if (errno == EINTR) @@ -144,7 +139,7 @@ int finish_command(struct child_process *cmd) error("waitpid failed (%s)", strerror(errno)); return -ERR_RUN_COMMAND_WAITPID; } - if (waiting != cmd->pid) + if (waiting != pid) return -ERR_RUN_COMMAND_WAITPID_WRONG_PID; if (WIFSIGNALED(status)) return -ERR_RUN_COMMAND_WAITPID_SIGNAL; @@ -158,6 +153,15 @@ int finish_command(struct child_process *cmd) } } +int finish_command(struct child_process *cmd) +{ + if (cmd->close_in) + close(cmd->in); + if (cmd->close_out) + close(cmd->out); + return wait_or_whine(cmd->pid); +} + int run_command(struct child_process *cmd) { int code = start_command(cmd); @@ -200,3 +204,35 @@ int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const cmd.env = env; return run_command(&cmd); } + +int start_async(struct async *async) +{ + int pipe_out[2]; + + if (pipe(pipe_out) < 0) { + return error("cannot create pipe: %s", strerror(errno)); + } + + async->pid = fork(); + if (async->pid < 0) { + error("fork (async) failed: %s", strerror(errno)); + close_pair(pipe_out); + return -1; + } + if (!async->pid) { + close(pipe_out[0]); + exit(!!async->proc(pipe_out[1], async->data)); + } + async->out = pipe_out[0]; + close(pipe_out[1]); + return 0; +} + +int finish_async(struct async *async) +{ + int ret = 0; + + if (wait_or_whine(async->pid)) + ret = error("waitpid (async) failed"); + return ret; +} diff --git a/run-command.h b/run-command.h index 35b9fb6..94e1e9d 100644 --- a/run-command.h +++ b/run-command.h @@ -43,4 +43,26 @@ int run_command_v_opt_cd(const char **argv, int opt, const char *dir); */ int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env); +/* + * The purpose of the following functions is to feed a pipe by running + * a function asynchronously and providing output that the caller reads. + * + * It is expected that no synchronization and mutual exclusion between + * the caller and the feed function is necessary so that the function + * can run in a thread without interfering with the caller. + */ +struct async { + /* + * proc writes to fd and closes it; + * returns 0 on success, non-zero on failure + */ + int (*proc)(int fd, void *data); + void *data; + int out; /* caller reads from here and closes it */ + pid_t pid; +}; + +int start_async(struct async *async); +int finish_async(struct async *async); + #endif
-- 1.5.3.2.141.g48f10