Preempt-RCU: implementation
This patch implements a new version of RCU which allows its read-side critical sections to be preempted. It uses a set of counter pairs to keep track of the read-side critical sections and flips them when all tasks exit read-side critical section. The details of this implementation can be found in this paper - http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf and the article- http://lwn.net/Articles/253651/ This patch was developed as a part of the -rt kernel development and meant to provide better latencies when read-side critical sections of RCU don't disable preemption. As a consequence of keeping track of RCU readers, the readers have a slight overhead (optimizations in the paper). This implementation co-exists with the "classic" RCU implementations and can be switched to at compiler. Also includes RCU tracing summarized in debugfs. [ akpm@linux-foundation.org: build fixes on non-preempt architectures ] Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com> Reviewed-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul E. McKenney
committed by
Ingo Molnar
Ingo Molnar
parent
e0ecfa7917
commit
e260be673a
816
kernel/rcupreempt.c
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816
kernel/rcupreempt.c
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@@ -0,0 +1,816 @@
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/*
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* Read-Copy Update mechanism for mutual exclusion, realtime implementation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright IBM Corporation, 2006
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*
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* Authors: Paul E. McKenney <paulmck@us.ibm.com>
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* With thanks to Esben Nielsen, Bill Huey, and Ingo Molnar
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* for pushing me away from locks and towards counters, and
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* to Suparna Bhattacharya for pushing me completely away
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* from atomic instructions on the read side.
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*
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* Papers: http://www.rdrop.com/users/paulmck/RCU
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*
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* Design Document: http://lwn.net/Articles/253651/
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU/ *.txt
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*
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/rcupdate.h>
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#include <asm/atomic.h>
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#include <linux/bitops.h>
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#include <linux/module.h>
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#include <linux/completion.h>
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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#include <linux/rcupdate.h>
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#include <linux/cpu.h>
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#include <linux/random.h>
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#include <linux/delay.h>
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#include <linux/byteorder/swabb.h>
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#include <linux/cpumask.h>
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#include <linux/rcupreempt_trace.h>
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/*
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* Macro that prevents the compiler from reordering accesses, but does
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* absolutely -nothing- to prevent CPUs from reordering. This is used
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* only to mediate communication between mainline code and hardware
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* interrupt and NMI handlers.
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*/
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#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
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/*
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* PREEMPT_RCU data structures.
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*/
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/*
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* GP_STAGES specifies the number of times the state machine has
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* to go through the all the rcu_try_flip_states (see below)
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* in a single Grace Period.
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*
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* GP in GP_STAGES stands for Grace Period ;)
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*/
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#define GP_STAGES 2
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struct rcu_data {
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spinlock_t lock; /* Protect rcu_data fields. */
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long completed; /* Number of last completed batch. */
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int waitlistcount;
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struct tasklet_struct rcu_tasklet;
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struct rcu_head *nextlist;
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struct rcu_head **nexttail;
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struct rcu_head *waitlist[GP_STAGES];
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struct rcu_head **waittail[GP_STAGES];
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struct rcu_head *donelist;
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struct rcu_head **donetail;
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long rcu_flipctr[2];
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#ifdef CONFIG_RCU_TRACE
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struct rcupreempt_trace trace;
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#endif /* #ifdef CONFIG_RCU_TRACE */
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};
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/*
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* States for rcu_try_flip() and friends.
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*/
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enum rcu_try_flip_states {
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/*
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* Stay here if nothing is happening. Flip the counter if somthing
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* starts happening. Denoted by "I"
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*/
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rcu_try_flip_idle_state,
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/*
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* Wait here for all CPUs to notice that the counter has flipped. This
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* prevents the old set of counters from ever being incremented once
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* we leave this state, which in turn is necessary because we cannot
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* test any individual counter for zero -- we can only check the sum.
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* Denoted by "A".
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*/
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rcu_try_flip_waitack_state,
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/*
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* Wait here for the sum of the old per-CPU counters to reach zero.
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* Denoted by "Z".
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*/
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rcu_try_flip_waitzero_state,
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/*
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* Wait here for each of the other CPUs to execute a memory barrier.
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* This is necessary to ensure that these other CPUs really have
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* completed executing their RCU read-side critical sections, despite
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* their CPUs wildly reordering memory. Denoted by "M".
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*/
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rcu_try_flip_waitmb_state,
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};
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struct rcu_ctrlblk {
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spinlock_t fliplock; /* Protect state-machine transitions. */
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long completed; /* Number of last completed batch. */
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enum rcu_try_flip_states rcu_try_flip_state; /* The current state of
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the rcu state machine */
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};
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static DEFINE_PER_CPU(struct rcu_data, rcu_data);
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static struct rcu_ctrlblk rcu_ctrlblk = {
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.fliplock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.fliplock),
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.completed = 0,
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.rcu_try_flip_state = rcu_try_flip_idle_state,
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};
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#ifdef CONFIG_RCU_TRACE
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static char *rcu_try_flip_state_names[] =
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{ "idle", "waitack", "waitzero", "waitmb" };
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#endif /* #ifdef CONFIG_RCU_TRACE */
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/*
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* Enum and per-CPU flag to determine when each CPU has seen
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* the most recent counter flip.
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*/
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enum rcu_flip_flag_values {
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rcu_flip_seen, /* Steady/initial state, last flip seen. */
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/* Only GP detector can update. */
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rcu_flipped /* Flip just completed, need confirmation. */
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/* Only corresponding CPU can update. */
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};
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static DEFINE_PER_CPU_SHARED_ALIGNED(enum rcu_flip_flag_values, rcu_flip_flag)
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= rcu_flip_seen;
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/*
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* Enum and per-CPU flag to determine when each CPU has executed the
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* needed memory barrier to fence in memory references from its last RCU
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* read-side critical section in the just-completed grace period.
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*/
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enum rcu_mb_flag_values {
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rcu_mb_done, /* Steady/initial state, no mb()s required. */
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/* Only GP detector can update. */
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rcu_mb_needed /* Flip just completed, need an mb(). */
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/* Only corresponding CPU can update. */
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};
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static DEFINE_PER_CPU_SHARED_ALIGNED(enum rcu_mb_flag_values, rcu_mb_flag)
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= rcu_mb_done;
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/*
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* RCU_DATA_ME: find the current CPU's rcu_data structure.
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* RCU_DATA_CPU: find the specified CPU's rcu_data structure.
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*/
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#define RCU_DATA_ME() (&__get_cpu_var(rcu_data))
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#define RCU_DATA_CPU(cpu) (&per_cpu(rcu_data, cpu))
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/*
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* Helper macro for tracing when the appropriate rcu_data is not
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* cached in a local variable, but where the CPU number is so cached.
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*/
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#define RCU_TRACE_CPU(f, cpu) RCU_TRACE(f, &(RCU_DATA_CPU(cpu)->trace));
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/*
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* Helper macro for tracing when the appropriate rcu_data is not
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* cached in a local variable.
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*/
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#define RCU_TRACE_ME(f) RCU_TRACE(f, &(RCU_DATA_ME()->trace));
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/*
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* Helper macro for tracing when the appropriate rcu_data is pointed
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* to by a local variable.
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*/
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#define RCU_TRACE_RDP(f, rdp) RCU_TRACE(f, &((rdp)->trace));
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/*
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* Return the number of RCU batches processed thus far. Useful
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* for debug and statistics.
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*/
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long rcu_batches_completed(void)
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{
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return rcu_ctrlblk.completed;
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed);
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EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
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void __rcu_read_lock(void)
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{
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int idx;
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struct task_struct *t = current;
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int nesting;
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nesting = ACCESS_ONCE(t->rcu_read_lock_nesting);
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if (nesting != 0) {
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/* An earlier rcu_read_lock() covers us, just count it. */
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t->rcu_read_lock_nesting = nesting + 1;
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} else {
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unsigned long flags;
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/*
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* We disable interrupts for the following reasons:
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* - If we get scheduling clock interrupt here, and we
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* end up acking the counter flip, it's like a promise
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* that we will never increment the old counter again.
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* Thus we will break that promise if that
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* scheduling clock interrupt happens between the time
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* we pick the .completed field and the time that we
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* increment our counter.
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*
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* - We don't want to be preempted out here.
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*
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* NMIs can still occur, of course, and might themselves
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* contain rcu_read_lock().
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*/
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local_irq_save(flags);
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/*
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* Outermost nesting of rcu_read_lock(), so increment
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* the current counter for the current CPU. Use volatile
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* casts to prevent the compiler from reordering.
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*/
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idx = ACCESS_ONCE(rcu_ctrlblk.completed) & 0x1;
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ACCESS_ONCE(RCU_DATA_ME()->rcu_flipctr[idx])++;
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/*
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* Now that the per-CPU counter has been incremented, we
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* are protected from races with rcu_read_lock() invoked
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* from NMI handlers on this CPU. We can therefore safely
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* increment the nesting counter, relieving further NMIs
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* of the need to increment the per-CPU counter.
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*/
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ACCESS_ONCE(t->rcu_read_lock_nesting) = nesting + 1;
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/*
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* Now that we have preventing any NMIs from storing
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* to the ->rcu_flipctr_idx, we can safely use it to
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* remember which counter to decrement in the matching
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* rcu_read_unlock().
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*/
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ACCESS_ONCE(t->rcu_flipctr_idx) = idx;
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local_irq_restore(flags);
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}
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}
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EXPORT_SYMBOL_GPL(__rcu_read_lock);
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void __rcu_read_unlock(void)
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{
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int idx;
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struct task_struct *t = current;
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int nesting;
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nesting = ACCESS_ONCE(t->rcu_read_lock_nesting);
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if (nesting > 1) {
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/*
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* We are still protected by the enclosing rcu_read_lock(),
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* so simply decrement the counter.
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*/
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t->rcu_read_lock_nesting = nesting - 1;
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} else {
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unsigned long flags;
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/*
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* Disable local interrupts to prevent the grace-period
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* detection state machine from seeing us half-done.
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* NMIs can still occur, of course, and might themselves
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* contain rcu_read_lock() and rcu_read_unlock().
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*/
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local_irq_save(flags);
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/*
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* Outermost nesting of rcu_read_unlock(), so we must
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* decrement the current counter for the current CPU.
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* This must be done carefully, because NMIs can
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* occur at any point in this code, and any rcu_read_lock()
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* and rcu_read_unlock() pairs in the NMI handlers
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* must interact non-destructively with this code.
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* Lots of volatile casts, and -very- careful ordering.
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*
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* Changes to this code, including this one, must be
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* inspected, validated, and tested extremely carefully!!!
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*/
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/*
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* First, pick up the index.
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*/
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idx = ACCESS_ONCE(t->rcu_flipctr_idx);
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/*
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* Now that we have fetched the counter index, it is
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* safe to decrement the per-task RCU nesting counter.
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* After this, any interrupts or NMIs will increment and
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* decrement the per-CPU counters.
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*/
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ACCESS_ONCE(t->rcu_read_lock_nesting) = nesting - 1;
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/*
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* It is now safe to decrement this task's nesting count.
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* NMIs that occur after this statement will route their
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* rcu_read_lock() calls through this "else" clause, and
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* will thus start incrementing the per-CPU counter on
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* their own. They will also clobber ->rcu_flipctr_idx,
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* but that is OK, since we have already fetched it.
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*/
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ACCESS_ONCE(RCU_DATA_ME()->rcu_flipctr[idx])--;
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local_irq_restore(flags);
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}
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}
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EXPORT_SYMBOL_GPL(__rcu_read_unlock);
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/*
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* If a global counter flip has occurred since the last time that we
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* advanced callbacks, advance them. Hardware interrupts must be
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* disabled when calling this function.
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*/
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static void __rcu_advance_callbacks(struct rcu_data *rdp)
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{
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int cpu;
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int i;
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int wlc = 0;
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if (rdp->completed != rcu_ctrlblk.completed) {
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if (rdp->waitlist[GP_STAGES - 1] != NULL) {
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*rdp->donetail = rdp->waitlist[GP_STAGES - 1];
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rdp->donetail = rdp->waittail[GP_STAGES - 1];
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RCU_TRACE_RDP(rcupreempt_trace_move2done, rdp);
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}
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for (i = GP_STAGES - 2; i >= 0; i--) {
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if (rdp->waitlist[i] != NULL) {
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rdp->waitlist[i + 1] = rdp->waitlist[i];
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rdp->waittail[i + 1] = rdp->waittail[i];
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wlc++;
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} else {
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rdp->waitlist[i + 1] = NULL;
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rdp->waittail[i + 1] =
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&rdp->waitlist[i + 1];
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}
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}
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if (rdp->nextlist != NULL) {
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rdp->waitlist[0] = rdp->nextlist;
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rdp->waittail[0] = rdp->nexttail;
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wlc++;
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rdp->nextlist = NULL;
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rdp->nexttail = &rdp->nextlist;
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RCU_TRACE_RDP(rcupreempt_trace_move2wait, rdp);
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} else {
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rdp->waitlist[0] = NULL;
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rdp->waittail[0] = &rdp->waitlist[0];
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}
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rdp->waitlistcount = wlc;
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rdp->completed = rcu_ctrlblk.completed;
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}
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/*
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* Check to see if this CPU needs to report that it has seen
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* the most recent counter flip, thereby declaring that all
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* subsequent rcu_read_lock() invocations will respect this flip.
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*/
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cpu = raw_smp_processor_id();
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if (per_cpu(rcu_flip_flag, cpu) == rcu_flipped) {
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smp_mb(); /* Subsequent counter accesses must see new value */
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per_cpu(rcu_flip_flag, cpu) = rcu_flip_seen;
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smp_mb(); /* Subsequent RCU read-side critical sections */
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/* seen -after- acknowledgement. */
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}
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}
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/*
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* Get here when RCU is idle. Decide whether we need to
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* move out of idle state, and return non-zero if so.
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* "Straightforward" approach for the moment, might later
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* use callback-list lengths, grace-period duration, or
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* some such to determine when to exit idle state.
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* Might also need a pre-idle test that does not acquire
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* the lock, but let's get the simple case working first...
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*/
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static int
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rcu_try_flip_idle(void)
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{
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int cpu;
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RCU_TRACE_ME(rcupreempt_trace_try_flip_i1);
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if (!rcu_pending(smp_processor_id())) {
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RCU_TRACE_ME(rcupreempt_trace_try_flip_ie1);
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return 0;
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}
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/*
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* Do the flip.
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*/
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RCU_TRACE_ME(rcupreempt_trace_try_flip_g1);
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rcu_ctrlblk.completed++; /* stands in for rcu_try_flip_g2 */
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/*
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* Need a memory barrier so that other CPUs see the new
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* counter value before they see the subsequent change of all
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* the rcu_flip_flag instances to rcu_flipped.
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*/
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smp_mb(); /* see above block comment. */
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/* Now ask each CPU for acknowledgement of the flip. */
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for_each_possible_cpu(cpu)
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per_cpu(rcu_flip_flag, cpu) = rcu_flipped;
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||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Wait for CPUs to acknowledge the flip.
|
||||
*/
|
||||
|
||||
static int
|
||||
rcu_try_flip_waitack(void)
|
||||
{
|
||||
int cpu;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_a1);
|
||||
for_each_possible_cpu(cpu)
|
||||
if (per_cpu(rcu_flip_flag, cpu) != rcu_flip_seen) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_ae1);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Make sure our checks above don't bleed into subsequent
|
||||
* waiting for the sum of the counters to reach zero.
|
||||
*/
|
||||
|
||||
smp_mb(); /* see above block comment. */
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_a2);
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Wait for collective ``last'' counter to reach zero,
|
||||
* then tell all CPUs to do an end-of-grace-period memory barrier.
|
||||
*/
|
||||
|
||||
static int
|
||||
rcu_try_flip_waitzero(void)
|
||||
{
|
||||
int cpu;
|
||||
int lastidx = !(rcu_ctrlblk.completed & 0x1);
|
||||
int sum = 0;
|
||||
|
||||
/* Check to see if the sum of the "last" counters is zero. */
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_z1);
|
||||
for_each_possible_cpu(cpu)
|
||||
sum += RCU_DATA_CPU(cpu)->rcu_flipctr[lastidx];
|
||||
if (sum != 0) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_ze1);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* This ensures that the other CPUs see the call for
|
||||
* memory barriers -after- the sum to zero has been
|
||||
* detected here
|
||||
*/
|
||||
smp_mb(); /* ^^^^^^^^^^^^ */
|
||||
|
||||
/* Call for a memory barrier from each CPU. */
|
||||
for_each_possible_cpu(cpu)
|
||||
per_cpu(rcu_mb_flag, cpu) = rcu_mb_needed;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_z2);
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Wait for all CPUs to do their end-of-grace-period memory barrier.
|
||||
* Return 0 once all CPUs have done so.
|
||||
*/
|
||||
|
||||
static int
|
||||
rcu_try_flip_waitmb(void)
|
||||
{
|
||||
int cpu;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_m1);
|
||||
for_each_possible_cpu(cpu)
|
||||
if (per_cpu(rcu_mb_flag, cpu) != rcu_mb_done) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_me1);
|
||||
return 0;
|
||||
}
|
||||
|
||||
smp_mb(); /* Ensure that the above checks precede any following flip. */
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_m2);
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Attempt a single flip of the counters. Remember, a single flip does
|
||||
* -not- constitute a grace period. Instead, the interval between
|
||||
* at least GP_STAGES consecutive flips is a grace period.
|
||||
*
|
||||
* If anyone is nuts enough to run this CONFIG_PREEMPT_RCU implementation
|
||||
* on a large SMP, they might want to use a hierarchical organization of
|
||||
* the per-CPU-counter pairs.
|
||||
*/
|
||||
static void rcu_try_flip(void)
|
||||
{
|
||||
unsigned long flags;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_1);
|
||||
if (unlikely(!spin_trylock_irqsave(&rcu_ctrlblk.fliplock, flags))) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_e1);
|
||||
return;
|
||||
}
|
||||
|
||||
/*
|
||||
* Take the next transition(s) through the RCU grace-period
|
||||
* flip-counter state machine.
|
||||
*/
|
||||
|
||||
switch (rcu_ctrlblk.rcu_try_flip_state) {
|
||||
case rcu_try_flip_idle_state:
|
||||
if (rcu_try_flip_idle())
|
||||
rcu_ctrlblk.rcu_try_flip_state =
|
||||
rcu_try_flip_waitack_state;
|
||||
break;
|
||||
case rcu_try_flip_waitack_state:
|
||||
if (rcu_try_flip_waitack())
|
||||
rcu_ctrlblk.rcu_try_flip_state =
|
||||
rcu_try_flip_waitzero_state;
|
||||
break;
|
||||
case rcu_try_flip_waitzero_state:
|
||||
if (rcu_try_flip_waitzero())
|
||||
rcu_ctrlblk.rcu_try_flip_state =
|
||||
rcu_try_flip_waitmb_state;
|
||||
break;
|
||||
case rcu_try_flip_waitmb_state:
|
||||
if (rcu_try_flip_waitmb())
|
||||
rcu_ctrlblk.rcu_try_flip_state =
|
||||
rcu_try_flip_idle_state;
|
||||
}
|
||||
spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, flags);
|
||||
}
|
||||
|
||||
/*
|
||||
* Check to see if this CPU needs to do a memory barrier in order to
|
||||
* ensure that any prior RCU read-side critical sections have committed
|
||||
* their counter manipulations and critical-section memory references
|
||||
* before declaring the grace period to be completed.
|
||||
*/
|
||||
static void rcu_check_mb(int cpu)
|
||||
{
|
||||
if (per_cpu(rcu_mb_flag, cpu) == rcu_mb_needed) {
|
||||
smp_mb(); /* Ensure RCU read-side accesses are visible. */
|
||||
per_cpu(rcu_mb_flag, cpu) = rcu_mb_done;
|
||||
}
|
||||
}
|
||||
|
||||
void rcu_check_callbacks(int cpu, int user)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
rcu_check_mb(cpu);
|
||||
if (rcu_ctrlblk.completed == rdp->completed)
|
||||
rcu_try_flip();
|
||||
spin_lock_irqsave(&rdp->lock, flags);
|
||||
RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
|
||||
__rcu_advance_callbacks(rdp);
|
||||
if (rdp->donelist == NULL) {
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
} else {
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
raise_softirq(RCU_SOFTIRQ);
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Needed by dynticks, to make sure all RCU processing has finished
|
||||
* when we go idle:
|
||||
*/
|
||||
void rcu_advance_callbacks(int cpu, int user)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
if (rcu_ctrlblk.completed == rdp->completed) {
|
||||
rcu_try_flip();
|
||||
if (rcu_ctrlblk.completed == rdp->completed)
|
||||
return;
|
||||
}
|
||||
spin_lock_irqsave(&rdp->lock, flags);
|
||||
RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
|
||||
__rcu_advance_callbacks(rdp);
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
}
|
||||
|
||||
static void rcu_process_callbacks(struct softirq_action *unused)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_head *next, *list;
|
||||
struct rcu_data *rdp = RCU_DATA_ME();
|
||||
|
||||
spin_lock_irqsave(&rdp->lock, flags);
|
||||
list = rdp->donelist;
|
||||
if (list == NULL) {
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
return;
|
||||
}
|
||||
rdp->donelist = NULL;
|
||||
rdp->donetail = &rdp->donelist;
|
||||
RCU_TRACE_RDP(rcupreempt_trace_done_remove, rdp);
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
while (list) {
|
||||
next = list->next;
|
||||
list->func(list);
|
||||
list = next;
|
||||
RCU_TRACE_ME(rcupreempt_trace_invoke);
|
||||
}
|
||||
}
|
||||
|
||||
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_data *rdp;
|
||||
|
||||
head->func = func;
|
||||
head->next = NULL;
|
||||
local_irq_save(flags);
|
||||
rdp = RCU_DATA_ME();
|
||||
spin_lock(&rdp->lock);
|
||||
__rcu_advance_callbacks(rdp);
|
||||
*rdp->nexttail = head;
|
||||
rdp->nexttail = &head->next;
|
||||
RCU_TRACE_RDP(rcupreempt_trace_next_add, rdp);
|
||||
spin_unlock(&rdp->lock);
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(call_rcu);
|
||||
|
||||
/*
|
||||
* Wait until all currently running preempt_disable() code segments
|
||||
* (including hardware-irq-disable segments) complete. Note that
|
||||
* in -rt this does -not- necessarily result in all currently executing
|
||||
* interrupt -handlers- having completed.
|
||||
*/
|
||||
void __synchronize_sched(void)
|
||||
{
|
||||
cpumask_t oldmask;
|
||||
int cpu;
|
||||
|
||||
if (sched_getaffinity(0, &oldmask) < 0)
|
||||
oldmask = cpu_possible_map;
|
||||
for_each_online_cpu(cpu) {
|
||||
sched_setaffinity(0, cpumask_of_cpu(cpu));
|
||||
schedule();
|
||||
}
|
||||
sched_setaffinity(0, oldmask);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(__synchronize_sched);
|
||||
|
||||
/*
|
||||
* Check to see if any future RCU-related work will need to be done
|
||||
* by the current CPU, even if none need be done immediately, returning
|
||||
* 1 if so. Assumes that notifiers would take care of handling any
|
||||
* outstanding requests from the RCU core.
|
||||
*
|
||||
* This function is part of the RCU implementation; it is -not-
|
||||
* an exported member of the RCU API.
|
||||
*/
|
||||
int rcu_needs_cpu(int cpu)
|
||||
{
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
return (rdp->donelist != NULL ||
|
||||
!!rdp->waitlistcount ||
|
||||
rdp->nextlist != NULL);
|
||||
}
|
||||
|
||||
int rcu_pending(int cpu)
|
||||
{
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
/* The CPU has at least one callback queued somewhere. */
|
||||
|
||||
if (rdp->donelist != NULL ||
|
||||
!!rdp->waitlistcount ||
|
||||
rdp->nextlist != NULL)
|
||||
return 1;
|
||||
|
||||
/* The RCU core needs an acknowledgement from this CPU. */
|
||||
|
||||
if ((per_cpu(rcu_flip_flag, cpu) == rcu_flipped) ||
|
||||
(per_cpu(rcu_mb_flag, cpu) == rcu_mb_needed))
|
||||
return 1;
|
||||
|
||||
/* This CPU has fallen behind the global grace-period number. */
|
||||
|
||||
if (rdp->completed != rcu_ctrlblk.completed)
|
||||
return 1;
|
||||
|
||||
/* Nothing needed from this CPU. */
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
void __init __rcu_init(void)
|
||||
{
|
||||
int cpu;
|
||||
int i;
|
||||
struct rcu_data *rdp;
|
||||
|
||||
printk(KERN_NOTICE "Preemptible RCU implementation.\n");
|
||||
for_each_possible_cpu(cpu) {
|
||||
rdp = RCU_DATA_CPU(cpu);
|
||||
spin_lock_init(&rdp->lock);
|
||||
rdp->completed = 0;
|
||||
rdp->waitlistcount = 0;
|
||||
rdp->nextlist = NULL;
|
||||
rdp->nexttail = &rdp->nextlist;
|
||||
for (i = 0; i < GP_STAGES; i++) {
|
||||
rdp->waitlist[i] = NULL;
|
||||
rdp->waittail[i] = &rdp->waitlist[i];
|
||||
}
|
||||
rdp->donelist = NULL;
|
||||
rdp->donetail = &rdp->donelist;
|
||||
rdp->rcu_flipctr[0] = 0;
|
||||
rdp->rcu_flipctr[1] = 0;
|
||||
}
|
||||
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
|
||||
}
|
||||
|
||||
/*
|
||||
* Deprecated, use synchronize_rcu() or synchronize_sched() instead.
|
||||
*/
|
||||
void synchronize_kernel(void)
|
||||
{
|
||||
synchronize_rcu();
|
||||
}
|
||||
|
||||
#ifdef CONFIG_RCU_TRACE
|
||||
long *rcupreempt_flipctr(int cpu)
|
||||
{
|
||||
return &RCU_DATA_CPU(cpu)->rcu_flipctr[0];
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_flipctr);
|
||||
|
||||
int rcupreempt_flip_flag(int cpu)
|
||||
{
|
||||
return per_cpu(rcu_flip_flag, cpu);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_flip_flag);
|
||||
|
||||
int rcupreempt_mb_flag(int cpu)
|
||||
{
|
||||
return per_cpu(rcu_mb_flag, cpu);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_mb_flag);
|
||||
|
||||
char *rcupreempt_try_flip_state_name(void)
|
||||
{
|
||||
return rcu_try_flip_state_names[rcu_ctrlblk.rcu_try_flip_state];
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_try_flip_state_name);
|
||||
|
||||
struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu)
|
||||
{
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
return &rdp->trace;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_trace_cpu);
|
||||
|
||||
#endif /* #ifdef RCU_TRACE */
|
||||
Reference in New Issue
Block a user