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2b38a833cd
Explicitly marking domains eligible for RCU synchronization. It's then forbidden to lock these domains in RCU critical section to avoid possible deadlock.
150 lines
3.6 KiB
C
150 lines
3.6 KiB
C
/*
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* BIRD Locking
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*
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* (c) 2020 Maria Matejka <mq@jmq.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*/
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#ifndef _GNU_SOURCE
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#define _GNU_SOURCE
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#endif
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#undef LOCAL_DEBUG
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#undef DEBUG_LOCKING
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#include "lib/birdlib.h"
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#include "lib/locking.h"
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#include "lib/resource.h"
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#include "lib/timer.h"
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#include "conf/conf.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <poll.h>
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#include <pthread.h>
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#include <semaphore.h>
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#include <stdatomic.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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/*
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* Locking subsystem
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*/
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_Thread_local struct lock_order locking_stack = {};
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_Thread_local struct domain_generic **last_locked = NULL;
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#define ASSERT_NO_LOCK ASSERT_DIE(last_locked == NULL)
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struct domain_generic {
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pthread_mutex_t mutex;
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uint order;
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_Bool forbidden_when_reading_rcu;
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struct domain_generic **prev;
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struct lock_order *locked_by;
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const char *name;
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pool *pool;
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};
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#define DOMAIN_INIT(_order, _allow_rcu) { \
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.mutex = PTHREAD_MUTEX_INITIALIZER, \
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.order = _order, \
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.forbidden_when_reading_rcu = !_allow_rcu, \
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}
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static struct domain_generic the_bird_domain_gen = DOMAIN_INIT(OFFSETOF(struct lock_order, the_bird), 1);
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DOMAIN(the_bird) the_bird_domain = { .the_bird = &the_bird_domain_gen };
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struct domain_generic *
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domain_new(uint order, _Bool allow_rcu)
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{
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ASSERT_DIE(order < sizeof(struct lock_order));
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struct domain_generic *dg = xmalloc(sizeof(struct domain_generic));
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*dg = (struct domain_generic) DOMAIN_INIT(order, allow_rcu);
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return dg;
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}
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void
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domain_free(struct domain_generic *dg)
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{
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pthread_mutex_destroy(&dg->mutex);
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xfree(dg);
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}
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const char *
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domain_name(struct domain_generic *dg)
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{
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return dg->name;
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}
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uint dg_order(struct domain_generic *dg)
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{
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return dg->order;
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}
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void
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domain_setup(struct domain_generic *dg, const char *name, pool *p)
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{
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ASSERT_DIE(dg->pool == NULL);
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dg->pool = p;
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dg->name = name;
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}
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void do_lock(struct domain_generic *dg, struct domain_generic **lsp)
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{
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struct lock_order stack_copy;
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memcpy(&stack_copy, &locking_stack, sizeof(stack_copy));
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struct domain_generic **lll = last_locked;
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if (dg->forbidden_when_reading_rcu)
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if (rcu_read_active())
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bug("Locking of this lock forbidden while RCU reader is active");
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else
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rcu_blocked++;
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if ((char *) lsp - (char *) &locking_stack != dg->order)
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bug("Trying to lock on bad position: order=%u, lsp=%p, base=%p", dg->order, lsp, &locking_stack);
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if (lsp <= last_locked)
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bug("Trying to lock in a bad order: %p %p", &stack_copy, lll);
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if (*lsp)
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bug("Inconsistent locking stack state on lock");
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btime lock_begin = current_time();
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pthread_mutex_lock(&dg->mutex);
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btime duration = current_time() - lock_begin;
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if (config && (duration > config->watchdog_warning))
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log(L_WARN "Locking of %s took %d ms", dg->name, (int) (duration TO_MS));
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if (dg->prev || dg->locked_by)
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bug("Previous unlock not finished correctly");
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dg->prev = last_locked;
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*lsp = dg;
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last_locked = lsp;
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dg->locked_by = &locking_stack;
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}
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void do_unlock(struct domain_generic *dg, struct domain_generic **lsp)
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{
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if ((char *) lsp - (char *) &locking_stack != dg->order)
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bug("Trying to unlock on bad position: order=%u, lsp=%p, base=%p", dg->order, lsp, &locking_stack);
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if (dg->locked_by != &locking_stack)
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bug("Inconsistent domain state on unlock");
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if ((last_locked != lsp) || (*lsp != dg))
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bug("Inconsistent locking stack state on unlock");
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dg->locked_by = NULL;
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last_locked = dg->prev;
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*lsp = NULL;
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dg->prev = NULL;
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pthread_mutex_unlock(&dg->mutex);
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if (dg->forbidden_when_reading_rcu)
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ASSERT_DIE(rcu_blocked--);
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}
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