Index: uspace/app/tester/Makefile =================================================================== --- uspace/app/tester/Makefile (revision b8d6783a99ca20a9a760d0859f69a1b5a920212a) +++ uspace/app/tester/Makefile (revision f76696fc11f7c97060cb5bfd3e184a0f78e483f9) @@ -50,4 +50,5 @@ vfs/vfs1.c \ ipc/ping_pong.c \ + ipc/starve.c \ loop/loop1.c \ mm/common.c \ Index: uspace/app/tester/ipc/starve.c =================================================================== --- uspace/app/tester/ipc/starve.c (revision f76696fc11f7c97060cb5bfd3e184a0f78e483f9) +++ uspace/app/tester/ipc/starve.c (revision f76696fc11f7c97060cb5bfd3e184a0f78e483f9) @@ -0,0 +1,84 @@ +/* + * Copyright (c) 2012 Vojtech Horky + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * - Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * - Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * - The name of the author may not be used to endorse or promote products + * derived from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include +#include +#include +#include +#include +#include "../tester.h" + +#define DURATION_SECS 30 + +const char *test_starve_ipc(void) +{ + const char *err = NULL; + console_ctrl_t *console = console_init(stdin, stdout); + if (console == NULL) { + return "Failed to init connection with console."; + } + + struct timeval start; + if (gettimeofday(&start, NULL) != 0) { + err = "Failed getting the time"; + goto leave; + } + + TPRINTF("Intensive computation shall be imagined (for %ds)...\n", DURATION_SECS); + TPRINTF("Press a key to terminate prematurely...\n"); + while (true) { + struct timeval now; + if (gettimeofday(&now, NULL) != 0) { + err = "Failed getting the time"; + goto leave; + } + + if (tv_sub(&now, &start) >= DURATION_SECS * 1000000L) + break; + + kbd_event_t ev; + suseconds_t timeout = 0; + bool has_event = console_get_kbd_event_timeout(console, &ev, &timeout); + if (has_event && (ev.type == KEY_PRESS)) { + TPRINTF("Key %d pressed, terminating.\n", ev.key); + break; + } + } + + // FIXME - unless a key was pressed, the answer leaked as no one + // will wait for it. + // We cannot use async_forget() directly, though. Something like + // console_forget_pending_kbd_event() shall come here. + + TPRINTF("Terminating...\n"); + +leave: + console_done(console); + + return err; +} Index: uspace/app/tester/ipc/starve.def =================================================================== --- uspace/app/tester/ipc/starve.def (revision f76696fc11f7c97060cb5bfd3e184a0f78e483f9) +++ uspace/app/tester/ipc/starve.def (revision f76696fc11f7c97060cb5bfd3e184a0f78e483f9) @@ -0,0 +1,6 @@ +{ + "starve", + "Demonstrate starving IPC", + &test_starve_ipc, + true +}, Index: uspace/app/tester/tester.c =================================================================== --- uspace/app/tester/tester.c (revision b8d6783a99ca20a9a760d0859f69a1b5a920212a) +++ uspace/app/tester/tester.c (revision f76696fc11f7c97060cb5bfd3e184a0f78e483f9) @@ -60,4 +60,5 @@ #include "vfs/vfs1.def" #include "ipc/ping_pong.def" +#include "ipc/starve.def" #include "loop/loop1.def" #include "mm/malloc1.def" Index: uspace/app/tester/tester.h =================================================================== --- uspace/app/tester/tester.h (revision b8d6783a99ca20a9a760d0859f69a1b5a920212a) +++ uspace/app/tester/tester.h (revision f76696fc11f7c97060cb5bfd3e184a0f78e483f9) @@ -93,4 +93,5 @@ extern const char *test_vfs1(void); extern const char *test_ping_pong(void); +extern const char *test_starve_ipc(void); extern const char *test_loop1(void); extern const char *test_malloc1(void); Index: uspace/lib/c/generic/async.c =================================================================== --- uspace/lib/c/generic/async.c (revision b8d6783a99ca20a9a760d0859f69a1b5a920212a) +++ uspace/lib/c/generic/async.c (revision f76696fc11f7c97060cb5bfd3e184a0f78e483f9) @@ -249,5 +249,5 @@ static void to_event_initialize(to_event_t *to) { - struct timeval tv = { 0 }; + struct timeval tv = { 0, 0 }; to->inlist = false; @@ -1017,4 +1017,5 @@ suseconds_t timeout; + unsigned int flags = SYNCH_FLAGS_NONE; if (!list_empty(&timeout_list)) { awaiter_t *waiter = list_get_instance( @@ -1027,17 +1028,30 @@ futex_up(&async_futex); handle_expired_timeouts(); - continue; - } else + /* + * Notice that even if the event(s) already + * expired (and thus the other fibril was + * supposed to be running already), + * we check for incoming IPC. + * + * Otherwise, a fibril that continuously + * creates (almost) expired events could + * prevent IPC retrieval from the kernel. + */ + timeout = 0; + flags = SYNCH_FLAGS_NON_BLOCKING; + + } else { timeout = tv_sub(&waiter->to_event.expires, &tv); - } else + futex_up(&async_futex); + } + } else { + futex_up(&async_futex); timeout = SYNCH_NO_TIMEOUT; - - futex_up(&async_futex); + } atomic_inc(&threads_in_ipc_wait); ipc_call_t call; - ipc_callid_t callid = ipc_wait_cycle(&call, timeout, - SYNCH_FLAGS_NONE); + ipc_callid_t callid = ipc_wait_cycle(&call, timeout, flags); atomic_dec(&threads_in_ipc_wait); @@ -1298,9 +1312,5 @@ amsg_t *msg = (amsg_t *) amsgid; - - /* TODO: Let it go through the event read at least once */ - if (timeout < 0) - return ETIMEOUT; - + futex_down(&async_futex); @@ -1313,7 +1323,31 @@ } + /* + * Negative timeout is converted to zero timeout to avoid + * using tv_add with negative augmenter. + */ + if (timeout < 0) + timeout = 0; + gettimeofday(&msg->wdata.to_event.expires, NULL); tv_add(&msg->wdata.to_event.expires, timeout); + /* + * Current fibril is inserted as waiting regardless of the + * "size" of the timeout. + * + * Checking for msg->done and immediately bailing out when + * timeout == 0 would mean that the manager fibril would never + * run (consider single threaded program). + * Thus the IPC answer would be never retrieved from the kernel. + * + * Notice that the actual delay would be very small because we + * - switch to manager fibril + * - the manager sees expired timeout + * - and thus adds us back to ready queue + * - manager switches back to some ready fibril + * (prior it, it checks for incoming IPC). + * + */ msg->wdata.fid = fibril_get_id(); msg->wdata.active = false;