AIO(7) Miscellaneous Information Manual AIO(7) aio - - POSIX - POSIX (AIO) -, (. ., ). -: , . POSIX AIO : aio_read(3) . read(2). aio_write(3) . write(2). aio_fsync(3) - . fsync(2) fdatasync(2). aio_error(3) -. aio_return(3) -. aio_suspend(3) , -. aio_cancel(3) - . lio_listio(3) - . aiocb (<< ->>) , -. , . : #include struct aiocb { /* The order of these fields is implementation-dependent */ int aio_fildes; /* File descriptor */ off_t aio_offset; /* File offset */ volatile void *aio_buf; /* Location of buffer */ size_t aio_nbytes; /* Length of transfer */ int aio_reqprio; /* Request priority */ struct sigevent aio_sigevent; /* Notification method */ int aio_lio_opcode; /* Operation to be performed; lio_listio() only */ /* Various implementation-internal fields not shown */ }; /* Operation codes for 'aio_lio_opcode': */ enum { LIO_READ, LIO_WRITE, LIO_NOP }; : aio_fildes , -. aio_offset , -. aio_buf , . aio_nbytes , aio_buf. aio_reqprio , , - ( pthread_setschedparam(3)). 0 , sysconf(_SC_AIO_PRIO_DELTA_MAX). . aio_sigevent This field is a structure that specifies how the caller is to be notified when the asynchronous I/O operation completes. Possible values for aio_sigevent.sigev_notify are SIGEV_NONE, SIGEV_SIGNAL, and SIGEV_THREAD. See sigevent(3type) for further details. aio_lio_opcode , ; lio_listio(3). , , GNU C POSIX AIO: aio_init(3) glibc POSIX AIO. EINVAL aio_reqprio aiocb 0 , , sysconf(_SC_AIO_PRIO_DELTA_MAX). POSIX.1-2008. POSIX.1-2001. glibc 2.1. ( memset(3)). , aio_buf, -. -. aiocb . Linux POSIX AIO glibc . , -- - . - ( io_submit(2), io_setup(2), io_cancel(2), io_destroy(2), io_getevents(2)), , POSIX AIO . , aio_read(3). , - aio_error(3). - . -, aio_return(3). The SIGQUIT signal (generated by typing control-\) causes the program to request cancelation of each of the outstanding requests using aio_cancel(3). . , <> <>. $ ./a.out /dev/stdin /dev/stdin /dev/stdin 3 /dev/stdin 4 aio_error(): 0 ( 3): 1 ( 4): abc - aio_error(): 0 ( 3): - 1 ( 4): aio_error(): 1 ( 4): x - aio_error(): 1 ( 4): - - aio_return(): 0 ( 3): 4 1 ( 4): 2 #include #include #include #include #include #include #include #define BUF_SIZE 20 /* Size of buffers for read operations */ #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0) struct ioRequest { /* Application-defined structure for tracking I/O requests */ int reqNum; int status; struct aiocb *aiocbp; }; static volatile sig_atomic_t gotSIGQUIT = 0; /* On delivery of SIGQUIT, we attempt to cancel all outstanding I/O requests */ static void /* Handler for SIGQUIT */ quitHandler(int sig) { gotSIGQUIT = 1; } #define IO_SIGNAL SIGUSR1 /* Signal used to notify I/O completion */ static void /* Handler for I/O completion signal */ aioSigHandler(int sig, siginfo_t *si, void *ucontext) { if (si->si_code == SI_ASYNCIO) { write(STDOUT_FILENO, "I/O completion signal received\n", 31); /* The corresponding ioRequest structure would be available as struct ioRequest *ioReq = si->si_value.sival_ptr; and the file descriptor would then be available via ioReq->aiocbp->aio_fildes */ } } int main(int argc, char *argv[]) { struct sigaction sa; int s; int numReqs; /* Total number of queued I/O requests */ int openReqs; /* Number of I/O requests still in progress */ if (argc < 2) { fprintf(stderr, "Usage: %s ...\n", argv[0]); exit(EXIT_FAILURE); } numReqs = argc - 1; /* Allocate our arrays. */ struct ioRequest *ioList = calloc(numReqs, sizeof(*ioList)); if (ioList == NULL) errExit("calloc"); struct aiocb *aiocbList = calloc(numReqs, sizeof(*aiocbList)); if (aiocbList == NULL) errExit("calloc"); /* Establish handlers for SIGQUIT and the I/O completion signal. */ sa.sa_flags = SA_RESTART; sigemptyset(&sa.sa_mask); sa.sa_handler = quitHandler; if (sigaction(SIGQUIT, &sa, NULL) == -1) errExit("sigaction"); sa.sa_flags = SA_RESTART | SA_SIGINFO; sa.sa_sigaction = aioSigHandler; if (sigaction(IO_SIGNAL, &sa, NULL) == -1) errExit("sigaction"); /* Open each file specified on the command line, and queue a read request on the resulting file descriptor. */ for (size_t j = 0; j < numReqs; j++) { ioList[j].reqNum = j; ioList[j].status = EINPROGRESS; ioList[j].aiocbp = &aiocbList[j]; ioList[j].aiocbp->aio_fildes = open(argv[j + 1], O_RDONLY); if (ioList[j].aiocbp->aio_fildes == -1) errExit("open"); printf("opened %s on descriptor %d\n", argv[j + 1], ioList[j].aiocbp->aio_fildes); ioList[j].aiocbp->aio_buf = malloc(BUF_SIZE); if (ioList[j].aiocbp->aio_buf == NULL) errExit("malloc"); ioList[j].aiocbp->aio_nbytes = BUF_SIZE; ioList[j].aiocbp->aio_reqprio = 0; ioList[j].aiocbp->aio_offset = 0; ioList[j].aiocbp->aio_sigevent.sigev_notify = SIGEV_SIGNAL; ioList[j].aiocbp->aio_sigevent.sigev_signo = IO_SIGNAL; ioList[j].aiocbp->aio_sigevent.sigev_value.sival_ptr = &ioList[j]; s = aio_read(ioList[j].aiocbp); if (s == -1) errExit("aio_read"); } openReqs = numReqs; /* Loop, monitoring status of I/O requests. */ while (openReqs > 0) { sleep(3); /* Delay between each monitoring step */ if (gotSIGQUIT) { /* On receipt of SIGQUIT, attempt to cancel each of the outstanding I/O requests, and display status returned from the cancelation requests. */ printf("got SIGQUIT; canceling I/O requests: \n"); for (size_t j = 0; j < numReqs; j++) { if (ioList[j].status == EINPROGRESS) { printf(" Request %zu on descriptor %d:", j, ioList[j].aiocbp->aio_fildes); s = aio_cancel(ioList[j].aiocbp->aio_fildes, ioList[j].aiocbp); if (s == AIO_CANCELED) printf("I/O canceled\n"); else if (s == AIO_NOTCANCELED) printf("I/O not canceled\n"); else if (s == AIO_ALLDONE) printf("I/O all done\n"); else perror("aio_cancel"); } } gotSIGQUIT = 0; } /* Check the status of each I/O request that is still in progress. */ printf("aio_error():\n"); for (size_t j = 0; j < numReqs; j++) { if (ioList[j].status == EINPROGRESS) { printf(" for request %zu (descriptor %d): ", j, ioList[j].aiocbp->aio_fildes); ioList[j].status = aio_error(ioList[j].aiocbp); switch (ioList[j].status) { case 0: printf("I/O succeeded\n"); break; case EINPROGRESS: printf("In progress\n"); break; case ECANCELED: printf("Canceled\n"); break; default: perror("aio_error"); break; } if (ioList[j].status != EINPROGRESS) openReqs--; } } } printf("All I/O requests completed\n"); /* Check status return of all I/O requests. */ printf("aio_return():\n"); for (size_t j = 0; j < numReqs; j++) { ssize_t s; s = aio_return(ioList[j].aiocbp); printf(" for request %zu (descriptor %d): %zd\n", j, ioList[j].aiocbp->aio_fildes, s); } exit(EXIT_SUCCESS); } io_cancel(2), io_destroy(2), io_getevents(2), io_setup(2), io_submit(2), aio_cancel(3), aio_error(3), aio_init(3), aio_read(3), aio_return(3), aio_write(3), lio_listio(3) <>, Bhattacharya, Pratt, Pulavarty, and Morgan, Proceedings of the Linux Symposium, 2003, () Dmitry Bolkhovskikh , Yuri Kozlov Kirill Rekhov ; GNU (GNU General Public License - GPL, 3 ) , - . - , , () () () <>. Linux 6.9.1 15 2024 . AIO(7)