X-Git-Url: http://mj.ucw.cz/gitweb/?a=blobdiff_plain;f=ucw%2Fmainloop.h;h=ae1c1e4a65600f44c4ad01d8c28c8f2c9f58fa15;hb=0f73a9b90ec53017512c34f7dab56be3a50d87b1;hp=90a4644d68dafb7ede7efd212f022bf202fe1060;hpb=952903e174bc0dc5e8077acf8b97afa1290c1120;p=libucw.git diff --git a/ucw/mainloop.h b/ucw/mainloop.h index 90a4644d..ae1c1e4a 100644 --- a/ucw/mainloop.h +++ b/ucw/mainloop.h @@ -1,7 +1,7 @@ /* * UCW Library -- Main Loop * - * (c) 2004--2005 Martin Mares + * (c) 2004--2011 Martin Mares * * This software may be freely distributed and used according to the terms * of the GNU Lesser General Public License. @@ -12,38 +12,147 @@ #include "ucw/clists.h" +#include + /*** - * [[conventions]] - * Conventions - * ----------- - * - * The descriptions of structures contain some fields marked with `[*]`. - * These are the only ones that are intended to be manipulated by the user. - * The remaining fields serve for internal use only and you must initialize them - * to zeroes. + * [[basic]] + * Basic operations + * ---------------- + * + * First of all, let us take a look at the basic operations with main loop contexts. ***/ +/** The main loop context **/ +struct main_context { + timestamp_t now; /* [*] Current time in milliseconds since the UNIX epoch. See main_get_time(). */ + ucw_time_t now_seconds; /* [*] Current time in seconds since the epoch. */ + timestamp_t idle_time; /* [*] Total time in milliseconds spent by waiting for events. */ + uns shutdown; /* [*] Setting this to nonzero forces the main_loop() function to terminate. */ + clist file_list; + clist file_active_list; + clist hook_list; + clist hook_done_list; + clist process_list; + clist signal_list; + uns file_cnt; + uns single_step; +#ifdef CONFIG_UCW_EPOLL + int epoll_fd; /* File descriptor used for epoll */ + struct epoll_event *epoll_events; + clist file_recalc_list; +#else + uns poll_table_obsolete; + struct pollfd *poll_table; + struct main_file **poll_file_table; +#endif + struct main_timer **timer_table; /* Growing array containing the heap of timers */ + sigset_t want_signals; + int sig_pipe_send; + int sig_pipe_recv; + struct main_file *sig_pipe_file; + struct main_signal *sigchld_handler; +}; + +struct main_context *main_new(void); /** Create a new context. **/ + +/** + * Delete a context, assuming it does have any event handlers attached. Does nothing if @m is NULL. + * It is allowed to call @main_delete() from a hook function of the same context, but you must + * never return to the main loop -- e.g., you can exit() the process instead. + **/ +void main_delete(struct main_context *m); + +/** + * Delete a context. If there are any event handlers attached, they are deactivated + * (but the responsibility to free the memory there were allocated from lies upon you). + * If there are any file handlers, the corresponding file descriptors are closed. + **/ +void main_destroy(struct main_context *m); + +/** Switch the current context of the calling thread. Returns the previous current context. **/ +struct main_context *main_switch_context(struct main_context *m); + +/** Return the current context. Dies if there is none or if the context has been deleted. **/ +struct main_context *main_current(void); + +/** Initialize the main loop module and create a top-level context. **/ +void main_init(void); + +/** Deinitialize the main loop module, calling @main_delete() on the top-level context. **/ +void main_cleanup(void); + +/** + * Deinitialize the main loop module, calling @main_destroy() on the top-level context. + * This is especially useful in a freshly forked-off child process. + **/ +void main_teardown(void); + +/** + * Start the event loop on the current context. + * It will watch the provided objects and call callbacks. + * Terminates when someone calls @main_shut_down(), + * or when all <> return <> + * or at last one <> returns <>. + **/ +void main_loop(void); + +/** + * Perform a single iteration of the main loop. + * Check if there are any events ready and process them. + * If there are none, do not wait. + **/ +void main_step(void); + +/** Ask the main loop to terminate at the nearest occasion. **/ +static inline void main_shut_down(void) +{ + main_current()->shutdown = 1; +} + +/** + * Show the current state of a given context (use @main_debug() for the current context). + * Available only if LibUCW has been compiled with `CONFIG_DEBUG`. + **/ +void main_debug_context(struct main_context *m); + +static inline void +main_debug(void) +{ + main_debug_context(main_current()); +} + /*** * [[time]] - * Time manipulation - * ----------------- + * Timers + * ------ * - * This part allows you to get the current time and request - * to have your function called when the time comes. + * The event loop provides the current time, measured as a 64-bit number + * of milliseconds since the system epoch (represented in the type `timestamp_t`). + * + * You can also register timers, which call a handler function at a given moment. + * The handler function must either call @timer_del() to delete the timer, or call + * @timer_add() with a different expiration time. ***/ -extern timestamp_t main_now; /** Current time in milliseconds since the UNIX epoch. See @main_get_time(). **/ -extern ucw_time_t main_now_seconds; /** Current time in seconds since the epoch. **/ -extern timestamp_t main_idle_time; /** Total time in milliseconds spent in the poll() call. **/ -extern clist main_timer_list, main_file_list, main_hook_list, main_process_list; +/** + * Get the current timestamp cached in the current context. It is refreshed in every + * iteration of the event loop, or explicitly by calling @main_get_time(). + **/ +static inline timestamp_t main_get_now(void) +{ + return main_current()->now; +} + +/** An analog of @main_get_now() returning the number of seconds since the system epoch. **/ +static inline ucw_time_t main_get_now_seconds(void) +{ + return main_current()->now_seconds; +} /** * This is a description of a timer. - * You fill in a handler function, any user-defined data you wish to pass - * to the handler, and then you invoke @timer_add(). - * - * The handler() function must either call @timer_del() to delete the timer, - * or call @timer_add() with a different expiration time. + * You define the handler function and possibly user-defined data you wish + * to pass to the handler, and then you invoke @timer_add(). **/ struct main_timer { cnode n; @@ -54,177 +163,221 @@ struct main_timer { }; /** - * Adds a new timer into the mainloop to be watched and called + * Add a new timer into the main loop to be watched and called * when it expires. It can also be used to modify an already running * timer. It is permitted (and usual) to call this function from the * timer's handler itself if you want the timer to trigger again. * - * The @expire parameter is absolute, just add <> if you need a relative timer. + * The @expire parameter is absolute, use @timer_add_rel() for a relative version. **/ void timer_add(struct main_timer *tm, timestamp_t expires); + +/** Like @timer_add(), but the expiration time is relative to the current time. **/ +void timer_add_rel(struct main_timer *tm, timestamp_t expires_delta); + /** - * Removes a timer from the active ones. It is permitted (and usual) to call + * Removes a timer from the active ones. It is permitted (and common) to call * this function from the timer's handler itself if you want to deactivate * the timer. **/ void timer_del(struct main_timer *tm); /** - * Forces refresh of <>. You do not usually - * need to call this, since it is called every time the loop polls for - * changes. It is here if you need extra precision or some of the + * Forces refresh of the current timestamp cached in the active context. + * You usually do not need to call this, since it is called every time the + * loop polls for events. It is here if you need extra precision or some of the * hooks takes a long time. **/ void main_get_time(void); +/** Show current state of a timer. Available only if LibUCW has been compiled with `CONFIG_DEBUG`. **/ +void timer_debug(struct main_timer *tm); + /*** * [[file]] * Activity on file descriptors * ---------------------------- * - * You can let the mainloop watch over a set of file descriptors - * for a changes. - * - * It supports two ways of use. With the first one, you provide - * low-level handlers for reading and writing (`read_handler` and - * `write_handler`). They will be called every time the file descriptor - * is ready to be read from or written to. + * You can ask the main loop to watch a set of file descriptors for activity. + * (This is a generalization of the select() and poll() system calls. Internally, + * it uses either poll() or the more efficient epoll().) * - * Return non-zero if you want to get the handler called again right now (you - * handled a block of data and expect more). If you return `0`, the hook will - * be called again in the next iteration, if it is still ready to be read/written. + * You create a <>, fill in a file descriptor + * and pointers to handler functions to be called when the descriptor becomes + * ready for reading and/or writing, and call @file_add(). When you need to + * modify the handlers (e.g., to set them to NULL if you are no longer interested + * in a given event), you should call @file_chg() to notify the main loop about + * the changes. * - * This way is suitable for listening sockets, interactive connections, where - * you need to parse everything that comes right away and similar cases. + * From within the handler functions, you are allowed to call @file_chg() and even + * @file_del(). * - * The second way is to ask mainloop to read or write a buffer of data. You - * provide a `read_done` or `write_done` handler respectively and call @file_read() - * or @file_write(). This is handy for data connections where you need to transfer - * data between two endpoints or for binary connections where the size of message - * is known in advance. + * The return value of a handler function should be either <> + * or <>. <> + * signals that the function would like to consume more data immediately + * (i.e., it wants to be called again soon, but the event loop can postpone it after + * processing other events to avoid starvation). <> + * tells that the handler wants to be called when the descriptor becomes ready again. * - * It is possible to combine both methods, but it may be tricky to do it right. + * For backward compatibility, 0 can be used instead of <> + * and 1 for <>. * - * Both ways use `error_handler` to notify you about errors. + * If you want to read/write fixed-size blocks of data asynchronously, the + * <> interface could be more convenient. ***/ /** - * If you want mainloop to watch a file descriptor, fill at last `fd` into this - * structure. To get any useful information from the mainloop, provide some handlers - * too. - * - * After that, insert it into the mainloop by calling @file_add(). + * This structure describes a file descriptor to be watched and the handlers + * to be called when the descriptor is ready for reading and/or writing. **/ struct main_file { cnode n; int fd; /* [*] File descriptor */ int (*read_handler)(struct main_file *fi); /* [*] To be called when ready for reading/writing; must call file_chg() afterwards */ int (*write_handler)(struct main_file *fi); - void (*error_handler)(struct main_file *fi, int cause); /* [*] Handler to call on errors */ void *data; /* [*] Data for use by the handlers */ - byte *rbuf; /* Read/write pointers for use by file_read/write */ - uns rpos, rlen; - byte *wbuf; - uns wpos, wlen; - void (*read_done)(struct main_file *fi); /* [*] Called when file_read is finished; rpos < rlen if EOF */ - void (*write_done)(struct main_file *fi); /* [*] Called when file_write is finished */ - struct main_timer timer; + uns events; +#ifdef CONFIG_UCW_EPOLL + uns last_want_events; +#else struct pollfd *pollfd; +#endif }; /** - * Specifies when or why an error happened. This is passed to the error handler. - * `errno` is still set to the original source of error. The only exception - * is `MFERR_TIMEOUT`, in which case `errno` is not set and the only possible - * cause of it is timeout on the file descriptor (see @file_set_timeout). - **/ -enum main_file_err_cause { - MFERR_READ, - MFERR_WRITE, - MFERR_TIMEOUT -}; - -/** - * Inserts a <> structure into the mainloop to be + * Insert a <> structure into the main loop to be * watched for activity. You can call this at any time, even inside a handler * (of course for a different file descriptor than the one of the handler). + * + * The file descriptor is automatically set to the non-blocking mode. **/ void file_add(struct main_file *fi); + /** - * Tells the mainloop the file has changed its state. Call it whenever you + * Tell the main loop that the file structure has changed. Call it whenever you * change any of the handlers. * * Can be called only on active files (only the ones added by @file_add()). **/ void file_chg(struct main_file *fi); + /** - * Removes a file from the watched set. You have to call this on closed files - * too, since the mainloop does not handle close in any way. + * Removes a file from the watched set. If you want to close a descriptor, + * please use this function first. * * Can be called from a handler. **/ void file_del(struct main_file *fi); + +/** Show current state of a file. Available only if LibUCW has been compiled with `CONFIG_DEBUG`. **/ +void file_debug(struct main_file *fi); + +/*** + * [[blockio]] + * Asynchronous block I/O + * ---------------------- + * + * If you are reading or writing fixed-size blocks of data, you can let the + * block I/O interface handle the boring routine of handling partial reads + * and writes for you. + * + * You just create <> and call + * @block_io_add() on it, which sets up some <>s internally. + * Then you can just call @block_io_read() or @block_io_write() to ask for + * reading or writing of a given block. When the operation is finished, + * your handler function is called. + * + * Additionally, the block I/O is equipped with a timer, which can be used + * to detect communication timeouts. The timer is not touched internally + * (except that it gets added and deleted at the right places), feel free + * to adjust it from your handler functions by @block_io_set_timeout(). + * When the timer expires, the error handler is automatically called with + * <>. + ***/ + +/** The block I/O structure. **/ +struct main_block_io { + struct main_file file; + byte *rbuf; /* Read/write pointers for use by file_read/write */ + uns rpos, rlen; + byte *wbuf; + uns wpos, wlen; + void (*read_done)(struct main_block_io *bio); /* [*] Called when file_read is finished; rpos < rlen if EOF */ + void (*write_done)(struct main_block_io *bio); /* [*] Called when file_write is finished */ + void (*error_handler)(struct main_block_io *bio, int cause); /* [*] Handler to call on errors */ + struct main_timer timer; + void *data; /* [*] Data for use by the handlers */ +}; + +/** Activate a block I/O structure. **/ +void block_io_add(struct main_block_io *bio, int fd); + +/** Deactivate a block I/O structure. **/ +void block_io_del(struct main_block_io *bio); + +/** + * Specifies when or why an error happened. This is passed to the error handler. + * `errno` is still set to the original source of error. The only exception + * is `BIO_ERR_TIMEOUT`, in which case `errno` is not set and the only possible + * cause of it is timeout of the timer associated with the block_io + * (see @block_io_set_timeout()). + **/ +enum block_io_err_cause { + BIO_ERR_READ, + BIO_ERR_WRITE, + BIO_ERR_TIMEOUT +}; + /** - * Asks the mainloop to read @len bytes of data from @fi into @buf. - * It cancels any previous unfinished read requested this way and overwrites - * `read_handler`. + * Ask the main loop to read @len bytes of data from @bio into @buf. + * It cancels any previous unfinished read requested in this way. * - * When the read is done, read_done() handler is called. If an EOF occurred, + * When the read is done, the read_done() handler is called. If an EOF occurred, * `rpos < rlen` (eg. not all data were read). * * Can be called from a handler. * - * You can use a call with zero @len to cancel current read, but all read data + * You can use a call with zero @len to cancel the current read, but all read data * will be thrown away. **/ -void file_read(struct main_file *fi, void *buf, uns len); +void block_io_read(struct main_block_io *bio, void *buf, uns len); + /** - * Requests that the mainloop writes @len bytes of data from @buf to @fi. + * Request that the main loop writes @len bytes of data from @buf to @bio. * Cancels any previous unfinished write and overwrites `write_handler`. * - * When it is written, write_done() handler is called. + * When it is written, the write_done() handler is called. * * Can be called from a handler. * * If you call it with zero @len, it will cancel the previous write, but note - * some data may already be written. + * that some data may already be written. **/ -void file_write(struct main_file *fi, void *buf, uns len); +void block_io_write(struct main_block_io *bio, void *buf, uns len); + /** - * Sets a timer for a file @fi. If the timer is not overwritten or disabled - * until @expires, the file timeouts and error_handler() is called with - * <>. - * - * The mainloop does not disable or reset it, when something happens, it just - * bundles a timer with the file. If you want to watch for inactivity, it is - * your task to reset it whenever your handler is called. + * Sets a timer for a file @bio. If the timer is not overwritten or disabled + * until @expires_delta milliseconds, the file timeouts and error_handler() is called with + * <>. A value of `0` stops the timer. * - * The @expires parameter is absolute (add <> if you - * need relative). The call and overwrites previously set timeout. Value of `0` - * disables the timeout (the <> will - * not trigger). + * Previous setting of the timeout on the same file will be overwritten. * * The use-cases for this are mainly sockets or pipes, when: * - * - You want to drop inactive connections (no data come or go for a given time, not + * - You want to drop inactive connections (no data comes in or out for a given time, not * incomplete messages). * - You want to enforce answer in a given time (for example authentication). - * - You give maximum time for a whole connection. + * - Watching maximum time for a whole connection. **/ -void file_set_timeout(struct main_file *fi, timestamp_t expires); -/** - * Closes all file descriptors known to mainloop. Often used between fork() - * and exec(). - **/ -void file_close_all(void); +void block_io_set_timeout(struct main_block_io *bio, timestamp_t expires_delta); /*** * [[hooks]] * Loop hooks * ---------- * - * The hooks are called whenever the mainloop perform an iteration. - * You can shutdown the mainloop from within them or request an iteration + * The hooks are called whenever the main loop performs an iteration. + * You can shutdown the main loop from within them or request an iteration * to happen without sleeping (just poll, no waiting for events). ***/ @@ -251,6 +404,9 @@ struct main_hook { * This will cause calling of all the hooks again soon. * - `HOOK_DONE` -- The loop will terminate if all hooks return this. * - `HOOK_SHUTDOWN` -- Shuts down the loop. + * + * The `HOOK_IDLE` and `HOOK_RETRY` constants are also used as return values + * of file handlers. **/ enum main_hook_return { HOOK_IDLE, @@ -261,15 +417,20 @@ enum main_hook_return { /** * Inserts a new hook into the loop. + * The hook will be scheduled at least once before next sleep. * May be called from inside a hook handler too. **/ void hook_add(struct main_hook *ho); + /** * Removes an existing hook from the loop. - * May be called from inside a hook handler (to delete itself or other hook). + * May be called from inside a hook handler (to delete itself or another hook). **/ void hook_del(struct main_hook *ho); +/** Show current state of a hook. Available only if LibUCW has been compiled with `CONFIG_DEBUG`. **/ +void hook_debug(struct main_hook *ho); + /*** * [[process]] * Child processes @@ -294,17 +455,19 @@ struct main_process { }; /** - * Asks the mainloop to watch this process. + * Asks the main loop to watch this process. * As it is done automatically in @process_fork(), you need this only * if you removed the process previously by @process_del(). **/ void process_add(struct main_process *mp); + /** * Removes the process from the watched set. This is done * automatically, when the process terminates, so you need it only * when you do not want to watch a running process any more. */ void process_del(struct main_process *mp); + /** * Forks and fills the @mp with information about the new process. * @@ -321,25 +484,50 @@ void process_del(struct main_process *mp); **/ int process_fork(struct main_process *mp); +/** Show current state of a process. Available only if LibUCW has been compiled with `CONFIG_DEBUG`. **/ +void process_debug(struct main_process *pr); + /*** - * [[control]] - * Control of the mainloop - * ----------------------- - * - * These functions control the mainloop as a whole. + * [[signal]] + * Synchronous delivery of signals + * ------------------------------- + * + * UNIX signals are delivered to processes in an asynchronous way: when a signal + * arrives (and it is not blocked), the process is interrupted and the corresponding + * signal handler function is called. However, most data structures and even most + * system library calls are not safe with respect to interrupts, so most program + * using signals contain subtle race conditions and may fail once in a long while. + * + * To avoid this problem, the event loop can be asked for synchronous delivery + * of signals. When a signal registered with @signal_add() arrives, it wakes up + * the loop (if it is not already awake) and it is processed in the same way + * as all other events. + * + * When used in a multi-threaded program, the signals are delivered to the thread + * which is currently using the particular main loop context. If the context is not + * current in any thread, the signals are blocked. + * + * As usually with UNIX signals, multiple instances of a single signal can be + * merged and delivered only once. (Some implementations of the main loop can even + * drop a signal completely during very intensive signal traffic, when an internal + * signal queue overflows.) ***/ -extern uns main_shutdown; /** Setting this to nonzero forces the @main_loop() function to terminate. **/ -void main_init(void); /** Initializes the mainloop structures. Call before any `*_add` function. **/ -/** - * Start the mainloop. - * It will watch the provided objects and call callbacks. - * Terminates when someone sets <> - * to nonzero, when all <> return - * <> or at last one <> - * returns <>. - **/ -void main_loop(void); -void main_debug(void); /** Prints a lot of debug information about current status of the mainloop. **/ +/** Description of a signal to catch. **/ +struct main_signal { + cnode n; + int signum; /* [*] Signal to catch */ + void (*handler)(struct main_signal *ms); /* [*] Called when the signal arrives */ + void *data; /* [*] For use by the handler */ +}; + +/** Request a signal to be caught and delivered synchronously. **/ +void signal_add(struct main_signal *ms); + +/** Cancel a request for signal catching. **/ +void signal_del(struct main_signal *ms); + +/** Show current state of a signal catcher. Available only if LibUCW has been compiled with `CONFIG_DEBUG`. **/ +void signal_debug(struct main_signal *sg); #endif