Date: Thu, 22 Feb 2018 03:23:43 +0000 (UTC) From: Alexander Motin <mav@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-vendor@freebsd.org Subject: svn commit: r329800 - in vendor-sys/illumos/dist/uts/common/fs/zfs: . sys Message-ID: <201802220323.w1M3Nhjg098916@repo.freebsd.org>
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Author: mav Date: Thu Feb 22 03:23:43 2018 New Revision: 329800 URL: https://svnweb.freebsd.org/changeset/base/329800 Log: Missed pieces of r329799. Added: vendor-sys/illumos/dist/uts/common/fs/zfs/sys/zthr.h (contents, props changed) vendor-sys/illumos/dist/uts/common/fs/zfs/zthr.c (contents, props changed) Added: vendor-sys/illumos/dist/uts/common/fs/zfs/sys/zthr.h ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ vendor-sys/illumos/dist/uts/common/fs/zfs/sys/zthr.h Thu Feb 22 03:23:43 2018 (r329800) @@ -0,0 +1,52 @@ +/* + * CDDL HEADER START + * + * This file and its contents are supplied under the terms of the + * Common Development and Distribution License ("CDDL"), version 1.0. + * You may only use this file in accordance with the terms of version + * 1.0 of the CDDL. + * + * A full copy of the text of the CDDL should have accompanied this + * source. A copy of the CDDL is also available via the Internet at + * http://www.illumos.org/license/CDDL. + * + * CDDL HEADER END + */ + + +/* + * Copyright (c) 2017 by Delphix. All rights reserved. + */ + +#ifndef _SYS_ZTHR_H +#define _SYS_ZTHR_H + +typedef struct zthr zthr_t; +typedef int (zthr_func_t)(void *, zthr_t *); +typedef boolean_t (zthr_checkfunc_t)(void *, zthr_t *); + +struct zthr { + kthread_t *zthr_thread; + kmutex_t zthr_lock; + kcondvar_t zthr_cv; + boolean_t zthr_cancel; + + zthr_checkfunc_t *zthr_checkfunc; + zthr_func_t *zthr_func; + void *zthr_arg; + int zthr_rc; +}; + +extern zthr_t *zthr_create(zthr_checkfunc_t checkfunc, + zthr_func_t *func, void *arg); +extern void zthr_exit(zthr_t *t, int rc); +extern void zthr_destroy(zthr_t *t); + +extern void zthr_wakeup(zthr_t *t); +extern int zthr_cancel(zthr_t *t); +extern void zthr_resume(zthr_t *t); + +extern boolean_t zthr_iscancelled(zthr_t *t); +extern boolean_t zthr_isrunning(zthr_t *t); + +#endif /* _SYS_ZTHR_H */ Added: vendor-sys/illumos/dist/uts/common/fs/zfs/zthr.c ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ vendor-sys/illumos/dist/uts/common/fs/zfs/zthr.c Thu Feb 22 03:23:43 2018 (r329800) @@ -0,0 +1,319 @@ +/* + * CDDL HEADER START + * + * This file and its contents are supplied under the terms of the + * Common Development and Distribution License ("CDDL"), version 1.0. + * You may only use this file in accordance with the terms of version + * 1.0 of the CDDL. + * + * A full copy of the text of the CDDL should have accompanied this + * source. A copy of the CDDL is also available via the Internet at + * http://www.illumos.org/license/CDDL. + * + * CDDL HEADER END + */ + +/* + * Copyright (c) 2017 by Delphix. All rights reserved. + */ + +/* + * ZTHR Infrastructure + * =================== + * + * ZTHR threads are used for isolated operations that span multiple txgs + * within a SPA. They generally exist from SPA creation/loading and until + * the SPA is exported/destroyed. The ideal requirements for an operation + * to be modeled with a zthr are the following: + * + * 1] The operation needs to run over multiple txgs. + * 2] There is be a single point of reference in memory or on disk that + * indicates whether the operation should run/is running or is + * stopped. + * + * If the operation satisfies the above then the following rules guarantee + * a certain level of correctness: + * + * 1] Any thread EXCEPT the zthr changes the work indicator from stopped + * to running but not the opposite. + * 2] Only the zthr can change the work indicator from running to stopped + * (e.g. when it is done) but not the opposite. + * + * This way a normal zthr cycle should go like this: + * + * 1] An external thread changes the work indicator from stopped to + * running and wakes up the zthr. + * 2] The zthr wakes up, checks the indicator and starts working. + * 3] When the zthr is done, it changes the indicator to stopped, allowing + * a new cycle to start. + * + * == ZTHR creation + * + * Every zthr needs three inputs to start running: + * + * 1] A user-defined checker function (checkfunc) that decides whether + * the zthr should start working or go to sleep. The function should + * return TRUE when the zthr needs to work or FALSE to let it sleep, + * and should adhere to the following signature: + * boolean_t checkfunc_name(void *args, zthr_t *t); + * + * 2] A user-defined ZTHR function (func) which the zthr executes when + * it is not sleeping. The function should adhere to the following + * signature type: + * int func_name(void *args, zthr_t *t); + * + * 3] A void args pointer that will be passed to checkfunc and func + * implicitly by the infrastructure. + * + * The reason why the above API needs two different functions, + * instead of one that both checks and does the work, has to do with + * the zthr's internal lock (zthr_lock) and the allowed cancellation + * windows. We want to hold the zthr_lock while running checkfunc + * but not while running func. This way the zthr can be cancelled + * while doing work and not while checking for work. + * + * To start a zthr: + * zthr_t *zthr_pointer = zthr_create(checkfunc, func, args); + * + * After that you should be able to wakeup, cancel, and resume the + * zthr from another thread using zthr_pointer. + * + * NOTE: ZTHR threads could potentially wake up spuriously and the + * user should take this into account when writing a checkfunc. + * [see ZTHR state transitions] + * + * == ZTHR cancellation + * + * ZTHR threads must be cancelled when their SPA is being exported + * or when they need to be paused so they don't interfere with other + * operations. + * + * To cancel a zthr: + * zthr_cancel(zthr_pointer); + * + * To resume it: + * zthr_resume(zthr_pointer); + * + * A zthr will implicitly check if it has received a cancellation + * signal every time func returns and everytime it wakes up [see ZTHR + * state transitions below]. + * + * At times, waiting for the zthr's func to finish its job may take + * time. This may be very time-consuming for some operations that + * need to cancel the SPA's zthrs (e.g spa_export). For this scenario + * the user can explicitly make their ZTHR function aware of incoming + * cancellation signals using zthr_iscancelled(). A common pattern for + * that looks like this: + * + * int + * func_name(void *args, zthr_t *t) + * { + * ... <unpack args> ... + * while (!work_done && !zthr_iscancelled(t)) { + * ... <do more work> ... + * } + * return (0); + * } + * + * == ZTHR exit + * + * For the rare cases where the zthr wants to stop running voluntarily + * while running its ZTHR function (func), we provide zthr_exit(). + * When a zthr has voluntarily stopped running, it can be resumed with + * zthr_resume(), just like it would if it was cancelled by some other + * thread. + * + * == ZTHR cleanup + * + * Cancelling a zthr doesn't clean up its metadata (internal locks, + * function pointers to func and checkfunc, etc..). This is because + * we want to keep them around in case we want to resume the execution + * of the zthr later. Similarly for zthrs that exit themselves. + * + * To completely cleanup a zthr, cancel it first to ensure that it + * is not running and then use zthr_destroy(). + * + * == ZTHR state transitions + * + * zthr creation + * + + * | + * | woke up + * | +--------------+ sleep + * | | ^ + * | | | + * | | | FALSE + * | | | + * v v FALSE + + * cancelled? +---------> checkfunc? + * + ^ + + * | | | + * | | | TRUE + * | | | + * | | func returned v + * | +---------------+ func + * | + * | TRUE + * | + * v + * zthr stopped running + * + */ + +#include <sys/zfs_context.h> +#include <sys/zthr.h> + +void +zthr_exit(zthr_t *t, int rc) +{ + ASSERT3P(t->zthr_thread, ==, curthread); + mutex_enter(&t->zthr_lock); + t->zthr_thread = NULL; + t->zthr_rc = rc; + cv_broadcast(&t->zthr_cv); + mutex_exit(&t->zthr_lock); + thread_exit(); +} + +static void +zthr_procedure(void *arg) +{ + zthr_t *t = arg; + int rc = 0; + + mutex_enter(&t->zthr_lock); + while (!t->zthr_cancel) { + if (t->zthr_checkfunc(t->zthr_arg, t)) { + mutex_exit(&t->zthr_lock); + rc = t->zthr_func(t->zthr_arg, t); + mutex_enter(&t->zthr_lock); + } else { + /* go to sleep */ + cv_wait(&t->zthr_cv, &t->zthr_lock); + } + } + mutex_exit(&t->zthr_lock); + + zthr_exit(t, rc); +} + +zthr_t * +zthr_create(zthr_checkfunc_t *checkfunc, zthr_func_t *func, void *arg) +{ + zthr_t *t = kmem_zalloc(sizeof (*t), KM_SLEEP); + mutex_init(&t->zthr_lock, NULL, MUTEX_DEFAULT, NULL); + cv_init(&t->zthr_cv, NULL, CV_DEFAULT, NULL); + + mutex_enter(&t->zthr_lock); + t->zthr_checkfunc = checkfunc; + t->zthr_func = func; + t->zthr_arg = arg; + + t->zthr_thread = thread_create(NULL, 0, zthr_procedure, t, + 0, &p0, TS_RUN, minclsyspri); + mutex_exit(&t->zthr_lock); + + return (t); +} + +void +zthr_destroy(zthr_t *t) +{ + VERIFY3P(t->zthr_thread, ==, NULL); + mutex_destroy(&t->zthr_lock); + cv_destroy(&t->zthr_cv); + kmem_free(t, sizeof (*t)); +} + +/* + * Note: If the zthr is not sleeping and misses the wakeup + * (e.g it is running its ZTHR function), it will check if + * there is work to do before going to sleep using its checker + * function [see ZTHR state transition in ZTHR block comment]. + * Thus, missing the wakeup still yields the expected behavior. + */ +void +zthr_wakeup(zthr_t *t) +{ + ASSERT3P(t->zthr_thread, !=, NULL); + + mutex_enter(&t->zthr_lock); + cv_broadcast(&t->zthr_cv); + mutex_exit(&t->zthr_lock); +} + +/* + * Note: If the zthr is not running (e.g. has been cancelled + * already), this is a no-op. + */ +int +zthr_cancel(zthr_t *t) +{ + int rc = 0; + + mutex_enter(&t->zthr_lock); + + /* broadcast in case the zthr is sleeping */ + cv_broadcast(&t->zthr_cv); + + t->zthr_cancel = B_TRUE; + while (t->zthr_thread != NULL) + cv_wait(&t->zthr_cv, &t->zthr_lock); + t->zthr_cancel = B_FALSE; + rc = t->zthr_rc; + mutex_exit(&t->zthr_lock); + + return (rc); +} + +void +zthr_resume(zthr_t *t) +{ + ASSERT3P(t->zthr_thread, ==, NULL); + + mutex_enter(&t->zthr_lock); + + ASSERT3P(&t->zthr_checkfunc, !=, NULL); + ASSERT3P(&t->zthr_func, !=, NULL); + ASSERT(!t->zthr_cancel); + + t->zthr_thread = thread_create(NULL, 0, zthr_procedure, t, + 0, &p0, TS_RUN, minclsyspri); + + mutex_exit(&t->zthr_lock); +} + +/* + * This function is intended to be used by the zthr itself + * to check if another thread has signal it to stop running. + * + * returns TRUE if we are in the middle of trying to cancel + * this thread. + * + * returns FALSE otherwise. + */ +boolean_t +zthr_iscancelled(zthr_t *t) +{ + boolean_t cancelled; + + ASSERT3P(t->zthr_thread, ==, curthread); + + mutex_enter(&t->zthr_lock); + cancelled = t->zthr_cancel; + mutex_exit(&t->zthr_lock); + + return (cancelled); +} + +boolean_t +zthr_isrunning(zthr_t *t) +{ + boolean_t running; + + mutex_enter(&t->zthr_lock); + running = (t->zthr_thread != NULL); + mutex_exit(&t->zthr_lock); + + return (running); +}
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