提交 1f889ec6 编写于 作者: L Linus Torvalds

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU updates from Ingo Molnar:
 "The main changes in this cycle are mostly related to preparatory work
  for the full-dynticks work:

   - Remove restrictions on no-CBs CPUs, make RCU_FAST_NO_HZ take
     advantage of numbered callbacks, do callback accelerations based on
     numbered callbacks.  Posted to LKML at
        https://lkml.org/lkml/2013/3/18/960

   - RCU documentation updates.  Posted to LKML at
        https://lkml.org/lkml/2013/3/18/570

   - Miscellaneous fixes.  Posted to LKML at
        https://lkml.org/lkml/2013/3/18/594"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
  rcu: Make rcu_accelerate_cbs() note need for future grace periods
  rcu: Abstract rcu_start_future_gp() from rcu_nocb_wait_gp()
  rcu: Rename n_nocb_gp_requests to need_future_gp
  rcu: Push lock release to rcu_start_gp()'s callers
  rcu: Repurpose no-CBs event tracing to future-GP events
  rcu: Rearrange locking in rcu_start_gp()
  rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks
  rcu: Accelerate RCU callbacks at grace-period end
  rcu: Export RCU_FAST_NO_HZ parameters to sysfs
  rcu: Distinguish "rcuo" kthreads by RCU flavor
  rcu: Add event tracing for no-CBs CPUs' grace periods
  rcu: Add event tracing for no-CBs CPUs' callback registration
  rcu: Introduce proper blocking to no-CBs kthreads GP waits
  rcu: Provide compile-time control for no-CBs CPUs
  rcu: Tone down debugging during boot-up and shutdown.
  rcu: Add softirq-stall indications to stall-warning messages
  rcu: Documentation update
  rcu: Make bugginess of code sample more evident
  rcu: Fix hlist_bl_set_first_rcu() annotation
  rcu: Delete unused rcu_node "wakemask" field
  ...
......@@ -217,9 +217,14 @@ over a rather long period of time, but improvements are always welcome!
whether the increased speed is worth it.
8. Although synchronize_rcu() is slower than is call_rcu(), it
usually results in simpler code. So, unless update performance
is critically important or the updaters cannot block,
synchronize_rcu() should be used in preference to call_rcu().
usually results in simpler code. So, unless update performance is
critically important, the updaters cannot block, or the latency of
synchronize_rcu() is visible from userspace, synchronize_rcu()
should be used in preference to call_rcu(). Furthermore,
kfree_rcu() usually results in even simpler code than does
synchronize_rcu() without synchronize_rcu()'s multi-millisecond
latency. So please take advantage of kfree_rcu()'s "fire and
forget" memory-freeing capabilities where it applies.
An especially important property of the synchronize_rcu()
primitive is that it automatically self-limits: if grace periods
......@@ -268,7 +273,8 @@ over a rather long period of time, but improvements are always welcome!
e. Periodically invoke synchronize_rcu(), permitting a limited
number of updates per grace period.
The same cautions apply to call_rcu_bh() and call_rcu_sched().
The same cautions apply to call_rcu_bh(), call_rcu_sched(),
call_srcu(), and kfree_rcu().
9. All RCU list-traversal primitives, which include
rcu_dereference(), list_for_each_entry_rcu(), and
......@@ -296,9 +302,9 @@ over a rather long period of time, but improvements are always welcome!
all currently executing rcu_read_lock()-protected RCU read-side
critical sections complete. It does -not- necessarily guarantee
that all currently running interrupts, NMIs, preempt_disable()
code, or idle loops will complete. Therefore, if you do not have
rcu_read_lock()-protected read-side critical sections, do -not-
use synchronize_rcu().
code, or idle loops will complete. Therefore, if your
read-side critical sections are protected by something other
than rcu_read_lock(), do -not- use synchronize_rcu().
Similarly, disabling preemption is not an acceptable substitute
for rcu_read_lock(). Code that attempts to use preemption
......@@ -401,9 +407,9 @@ over a rather long period of time, but improvements are always welcome!
read-side critical sections. It is the responsibility of the
RCU update-side primitives to deal with this.
17. Use CONFIG_PROVE_RCU, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and
the __rcu sparse checks to validate your RCU code. These
can help find problems as follows:
17. Use CONFIG_PROVE_RCU, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and the
__rcu sparse checks (enabled by CONFIG_SPARSE_RCU_POINTER) to
validate your RCU code. These can help find problems as follows:
CONFIG_PROVE_RCU: check that accesses to RCU-protected data
structures are carried out under the proper RCU
......
......@@ -64,6 +64,11 @@ checking of rcu_dereference() primitives:
but retain the compiler constraints that prevent duplicating
or coalescsing. This is useful when when testing the
value of the pointer itself, for example, against NULL.
rcu_access_index(idx):
Return the value of the index and omit all barriers, but
retain the compiler constraints that prevent duplicating
or coalescsing. This is useful when when testing the
value of the index itself, for example, against -1.
The rcu_dereference_check() check expression can be any boolean
expression, but would normally include a lockdep expression. However,
......
......@@ -79,7 +79,20 @@ complete. Pseudo-code using rcu_barrier() is as follows:
2. Execute rcu_barrier().
3. Allow the module to be unloaded.
The rcutorture module makes use of rcu_barrier in its exit function
There are also rcu_barrier_bh(), rcu_barrier_sched(), and srcu_barrier()
functions for the other flavors of RCU, and you of course must match
the flavor of rcu_barrier() with that of call_rcu(). If your module
uses multiple flavors of call_rcu(), then it must also use multiple
flavors of rcu_barrier() when unloading that module. For example, if
it uses call_rcu_bh(), call_srcu() on srcu_struct_1, and call_srcu() on
srcu_struct_2(), then the following three lines of code will be required
when unloading:
1 rcu_barrier_bh();
2 srcu_barrier(&srcu_struct_1);
3 srcu_barrier(&srcu_struct_2);
The rcutorture module makes use of rcu_barrier() in its exit function
as follows:
1 static void
......
......@@ -92,14 +92,14 @@ If the CONFIG_RCU_CPU_STALL_INFO kernel configuration parameter is set,
more information is printed with the stall-warning message, for example:
INFO: rcu_preempt detected stall on CPU
0: (63959 ticks this GP) idle=241/3fffffffffffffff/0
0: (63959 ticks this GP) idle=241/3fffffffffffffff/0 softirq=82/543
(t=65000 jiffies)
In kernels with CONFIG_RCU_FAST_NO_HZ, even more information is
printed:
INFO: rcu_preempt detected stall on CPU
0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 drain=0 . timer not pending
0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 softirq=82/543 last_accelerate: a345/d342 nonlazy_posted: 25 .D
(t=65000 jiffies)
The "(64628 ticks this GP)" indicates that this CPU has taken more
......@@ -116,13 +116,28 @@ number between the two "/"s is the value of the nesting, which will
be a small positive number if in the idle loop and a very large positive
number (as shown above) otherwise.
For CONFIG_RCU_FAST_NO_HZ kernels, the "drain=0" indicates that the CPU is
not in the process of trying to force itself into dyntick-idle state, the
"." indicates that the CPU has not given up forcing RCU into dyntick-idle
mode (it would be "H" otherwise), and the "timer not pending" indicates
that the CPU has not recently forced RCU into dyntick-idle mode (it
would otherwise indicate the number of microseconds remaining in this
forced state).
The "softirq=" portion of the message tracks the number of RCU softirq
handlers that the stalled CPU has executed. The number before the "/"
is the number that had executed since boot at the time that this CPU
last noted the beginning of a grace period, which might be the current
(stalled) grace period, or it might be some earlier grace period (for
example, if the CPU might have been in dyntick-idle mode for an extended
time period. The number after the "/" is the number that have executed
since boot until the current time. If this latter number stays constant
across repeated stall-warning messages, it is possible that RCU's softirq
handlers are no longer able to execute on this CPU. This can happen if
the stalled CPU is spinning with interrupts are disabled, or, in -rt
kernels, if a high-priority process is starving RCU's softirq handler.
For CONFIG_RCU_FAST_NO_HZ kernels, the "last_accelerate:" prints the
low-order 16 bits (in hex) of the jiffies counter when this CPU last
invoked rcu_try_advance_all_cbs() from rcu_needs_cpu() or last invoked
rcu_accelerate_cbs() from rcu_prepare_for_idle(). The "nonlazy_posted:"
prints the number of non-lazy callbacks posted since the last call to
rcu_needs_cpu(). Finally, an "L" indicates that there are currently
no non-lazy callbacks ("." is printed otherwise, as shown above) and
"D" indicates that dyntick-idle processing is enabled ("." is printed
otherwise, for example, if disabled via the "nohz=" kernel boot parameter).
Multiple Warnings From One Stall
......
......@@ -265,9 +265,9 @@ rcu_dereference()
rcu_read_lock();
p = rcu_dereference(head.next);
rcu_read_unlock();
x = p->address;
x = p->address; /* BUG!!! */
rcu_read_lock();
y = p->data;
y = p->data; /* BUG!!! */
rcu_read_unlock();
Holding a reference from one RCU read-side critical section
......
......@@ -2499,9 +2499,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
In kernels built with CONFIG_RCU_NOCB_CPU=y, set
the specified list of CPUs to be no-callback CPUs.
Invocation of these CPUs' RCU callbacks will
be offloaded to "rcuoN" kthreads created for
that purpose. This reduces OS jitter on the
be offloaded to "rcuox/N" kthreads created for
that purpose, where "x" is "b" for RCU-bh, "p"
for RCU-preempt, and "s" for RCU-sched, and "N"
is the CPU number. This reduces OS jitter on the
offloaded CPUs, which can be useful for HPC and
real-time workloads. It can also improve energy
efficiency for asymmetric multiprocessors.
......@@ -2525,6 +2528,17 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
leaf rcu_node structure. Useful for very large
systems.
rcutree.jiffies_till_first_fqs= [KNL,BOOT]
Set delay from grace-period initialization to
first attempt to force quiescent states.
Units are jiffies, minimum value is zero,
and maximum value is HZ.
rcutree.jiffies_till_next_fqs= [KNL,BOOT]
Set delay between subsequent attempts to force
quiescent states. Units are jiffies, minimum
value is one, and maximum value is HZ.
rcutree.qhimark= [KNL,BOOT]
Set threshold of queued
RCU callbacks over which batch limiting is disabled.
......@@ -2539,16 +2553,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
Set timeout for RCU CPU stall warning messages.
rcutree.jiffies_till_first_fqs= [KNL,BOOT]
Set delay from grace-period initialization to
first attempt to force quiescent states.
Units are jiffies, minimum value is zero,
and maximum value is HZ.
rcutree.rcu_idle_gp_delay= [KNL,BOOT]
Set wakeup interval for idle CPUs that have
RCU callbacks (RCU_FAST_NO_HZ=y).
rcutree.jiffies_till_next_fqs= [KNL,BOOT]
Set delay between subsequent attempts to force
quiescent states. Units are jiffies, minimum
value is one, and maximum value is HZ.
rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
Set wakeup interval for idle CPUs that have
only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
Lazy RCU callbacks are those which RCU can
prove do nothing more than free memory.
rcutorture.fqs_duration= [KNL,BOOT]
Set duration of force_quiescent_state bursts.
......
......@@ -125,6 +125,11 @@ static inline void hlist_bl_unlock(struct hlist_bl_head *b)
__bit_spin_unlock(0, (unsigned long *)b);
}
static inline bool hlist_bl_is_locked(struct hlist_bl_head *b)
{
return bit_spin_is_locked(0, (unsigned long *)b);
}
/**
* hlist_bl_for_each_entry - iterate over list of given type
* @tpos: the type * to use as a loop cursor.
......
......@@ -20,7 +20,7 @@ static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
{
return (struct hlist_bl_node *)
((unsigned long)rcu_dereference(h->first) & ~LIST_BL_LOCKMASK);
((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
}
/**
......
......@@ -80,6 +80,7 @@ extern void do_trace_rcu_torture_read(char *rcutorturename,
#define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b))
#define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b))
#define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b))
#define ulong2long(a) (*(long *)(&(a)))
/* Exported common interfaces */
......
......@@ -71,6 +71,58 @@ TRACE_EVENT(rcu_grace_period,
__entry->rcuname, __entry->gpnum, __entry->gpevent)
);
/*
* Tracepoint for future grace-period events, including those for no-callbacks
* CPUs. The caller should pull the data from the rcu_node structure,
* other than rcuname, which comes from the rcu_state structure, and event,
* which is one of the following:
*
* "Startleaf": Request a nocb grace period based on leaf-node data.
* "Startedleaf": Leaf-node start proved sufficient.
* "Startedleafroot": Leaf-node start proved sufficient after checking root.
* "Startedroot": Requested a nocb grace period based on root-node data.
* "StartWait": Start waiting for the requested grace period.
* "ResumeWait": Resume waiting after signal.
* "EndWait": Complete wait.
* "Cleanup": Clean up rcu_node structure after previous GP.
* "CleanupMore": Clean up, and another no-CB GP is needed.
*/
TRACE_EVENT(rcu_future_grace_period,
TP_PROTO(char *rcuname, unsigned long gpnum, unsigned long completed,
unsigned long c, u8 level, int grplo, int grphi,
char *gpevent),
TP_ARGS(rcuname, gpnum, completed, c, level, grplo, grphi, gpevent),
TP_STRUCT__entry(
__field(char *, rcuname)
__field(unsigned long, gpnum)
__field(unsigned long, completed)
__field(unsigned long, c)
__field(u8, level)
__field(int, grplo)
__field(int, grphi)
__field(char *, gpevent)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->gpnum = gpnum;
__entry->completed = completed;
__entry->c = c;
__entry->level = level;
__entry->grplo = grplo;
__entry->grphi = grphi;
__entry->gpevent = gpevent;
),
TP_printk("%s %lu %lu %lu %u %d %d %s",
__entry->rcuname, __entry->gpnum, __entry->completed,
__entry->c, __entry->level, __entry->grplo, __entry->grphi,
__entry->gpevent)
);
/*
* Tracepoint for grace-period-initialization events. These are
* distinguished by the type of RCU, the new grace-period number, the
......@@ -601,6 +653,9 @@ TRACE_EVENT(rcu_barrier,
#define trace_rcu_grace_period(rcuname, gpnum, gpevent) do { } while (0)
#define trace_rcu_grace_period_init(rcuname, gpnum, level, grplo, grphi, \
qsmask) do { } while (0)
#define trace_rcu_future_grace_period(rcuname, gpnum, completed, c, \
level, grplo, grphi, event) \
do { } while (0)
#define trace_rcu_preempt_task(rcuname, pid, gpnum) do { } while (0)
#define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)
#define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, \
......
......@@ -578,13 +578,16 @@ config RCU_FAST_NO_HZ
depends on NO_HZ && SMP
default n
help
This option causes RCU to attempt to accelerate grace periods in
order to allow CPUs to enter dynticks-idle state more quickly.
On the other hand, this option increases the overhead of the
dynticks-idle checking, thus degrading scheduling latency.
This option permits CPUs to enter dynticks-idle state even if
they have RCU callbacks queued, and prevents RCU from waking
these CPUs up more than roughly once every four jiffies (by
default, you can adjust this using the rcutree.rcu_idle_gp_delay
parameter), thus improving energy efficiency. On the other
hand, this option increases the duration of RCU grace periods,
for example, slowing down synchronize_rcu().
Say Y if energy efficiency is critically important, and you don't
care about real-time response.
Say Y if energy efficiency is critically important, and you
don't care about increased grace-period durations.
Say N if you are unsure.
......@@ -651,7 +654,7 @@ config RCU_BOOST_DELAY
Accept the default if unsure.
config RCU_NOCB_CPU
bool "Offload RCU callback processing from boot-selected CPUs"
bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
depends on TREE_RCU || TREE_PREEMPT_RCU
default n
help
......@@ -662,16 +665,56 @@ config RCU_NOCB_CPU
This option offloads callback invocation from the set of
CPUs specified at boot time by the rcu_nocbs parameter.
For each such CPU, a kthread ("rcuoN") will be created to
invoke callbacks, where the "N" is the CPU being offloaded.
Nothing prevents this kthread from running on the specified
CPUs, but (1) the kthreads may be preempted between each
callback, and (2) affinity or cgroups can be used to force
the kthreads to run on whatever set of CPUs is desired.
Say Y here if you want reduced OS jitter on selected CPUs.
For each such CPU, a kthread ("rcuox/N") will be created to
invoke callbacks, where the "N" is the CPU being offloaded,
and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
"s" for RCU-sched. Nothing prevents this kthread from running
on the specified CPUs, but (1) the kthreads may be preempted
between each callback, and (2) affinity or cgroups can be used
to force the kthreads to run on whatever set of CPUs is desired.
Say Y here if you want to help to debug reduced OS jitter.
Say N here if you are unsure.
choice
prompt "Build-forced no-CBs CPUs"
default RCU_NOCB_CPU_NONE
help
This option allows no-CBs CPUs to be specified at build time.
Additional no-CBs CPUs may be specified by the rcu_nocbs=
boot parameter.
config RCU_NOCB_CPU_NONE
bool "No build_forced no-CBs CPUs"
depends on RCU_NOCB_CPU
help
This option does not force any of the CPUs to be no-CBs CPUs.
Only CPUs designated by the rcu_nocbs= boot parameter will be
no-CBs CPUs.
config RCU_NOCB_CPU_ZERO
bool "CPU 0 is a build_forced no-CBs CPU"
depends on RCU_NOCB_CPU
help
This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
may be designated as no-CBs CPUs using the rcu_nocbs= boot
parameter will be no-CBs CPUs.
Select this if CPU 0 needs to be a no-CBs CPU for real-time
or energy-efficiency reasons.
config RCU_NOCB_CPU_ALL
bool "All CPUs are build_forced no-CBs CPUs"
depends on RCU_NOCB_CPU
help
This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
boot parameter will be ignored.
Select this if all CPUs need to be no-CBs CPUs for real-time
or energy-efficiency reasons.
endchoice
endmenu # "RCU Subsystem"
config IKCONFIG
......
......@@ -64,7 +64,7 @@
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
#define RCU_STATE_INITIALIZER(sname, cr) { \
#define RCU_STATE_INITIALIZER(sname, sabbr, cr) { \
.level = { &sname##_state.node[0] }, \
.call = cr, \
.fqs_state = RCU_GP_IDLE, \
......@@ -76,13 +76,14 @@ static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
.onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
.name = #sname, \
.abbr = sabbr, \
}
struct rcu_state rcu_sched_state =
RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched);
RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh);
struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
static struct rcu_state *rcu_state;
......@@ -223,6 +224,8 @@ static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
module_param(jiffies_till_first_fqs, ulong, 0644);
module_param(jiffies_till_next_fqs, ulong, 0644);
static void rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp);
static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *));
static void force_quiescent_state(struct rcu_state *rsp);
static int rcu_pending(int cpu);
......@@ -310,6 +313,8 @@ cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
if (rcu_gp_in_progress(rsp))
return 0; /* No, a grace period is already in progress. */
if (rcu_nocb_needs_gp(rsp))
return 1; /* Yes, a no-CBs CPU needs one. */
if (!rdp->nxttail[RCU_NEXT_TAIL])
return 0; /* No, this is a no-CBs (or offline) CPU. */
if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
......@@ -1035,10 +1040,11 @@ static void init_callback_list(struct rcu_data *rdp)
{
int i;
if (init_nocb_callback_list(rdp))
return;
rdp->nxtlist = NULL;
for (i = 0; i < RCU_NEXT_SIZE; i++)
rdp->nxttail[i] = &rdp->nxtlist;
init_nocb_callback_list(rdp);
}
/*
......@@ -1070,6 +1076,120 @@ static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
return rnp->completed + 2;
}
/*
* Trace-event helper function for rcu_start_future_gp() and
* rcu_nocb_wait_gp().
*/
static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
unsigned long c, char *s)
{
trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
rnp->completed, c, rnp->level,
rnp->grplo, rnp->grphi, s);
}
/*
* Start some future grace period, as needed to handle newly arrived
* callbacks. The required future grace periods are recorded in each
* rcu_node structure's ->need_future_gp field.
*
* The caller must hold the specified rcu_node structure's ->lock.
*/
static unsigned long __maybe_unused
rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp)
{
unsigned long c;
int i;
struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
/*
* Pick up grace-period number for new callbacks. If this
* grace period is already marked as needed, return to the caller.
*/
c = rcu_cbs_completed(rdp->rsp, rnp);
trace_rcu_future_gp(rnp, rdp, c, "Startleaf");
if (rnp->need_future_gp[c & 0x1]) {
trace_rcu_future_gp(rnp, rdp, c, "Prestartleaf");
return c;
}
/*
* If either this rcu_node structure or the root rcu_node structure
* believe that a grace period is in progress, then we must wait
* for the one following, which is in "c". Because our request
* will be noticed at the end of the current grace period, we don't
* need to explicitly start one.
*/
if (rnp->gpnum != rnp->completed ||
ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) {
rnp->need_future_gp[c & 0x1]++;
trace_rcu_future_gp(rnp, rdp, c, "Startedleaf");
return c;
}
/*
* There might be no grace period in progress. If we don't already
* hold it, acquire the root rcu_node structure's lock in order to
* start one (if needed).
*/
if (rnp != rnp_root)
raw_spin_lock(&rnp_root->lock);
/*
* Get a new grace-period number. If there really is no grace
* period in progress, it will be smaller than the one we obtained
* earlier. Adjust callbacks as needed. Note that even no-CBs
* CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed.
*/
c = rcu_cbs_completed(rdp->rsp, rnp_root);
for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++)
if (ULONG_CMP_LT(c, rdp->nxtcompleted[i]))
rdp->nxtcompleted[i] = c;
/*
* If the needed for the required grace period is already
* recorded, trace and leave.
*/
if (rnp_root->need_future_gp[c & 0x1]) {
trace_rcu_future_gp(rnp, rdp, c, "Prestartedroot");
goto unlock_out;
}
/* Record the need for the future grace period. */
rnp_root->need_future_gp[c & 0x1]++;
/* If a grace period is not already in progress, start one. */
if (rnp_root->gpnum != rnp_root->completed) {
trace_rcu_future_gp(rnp, rdp, c, "Startedleafroot");
} else {
trace_rcu_future_gp(rnp, rdp, c, "Startedroot");
rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp);
}
unlock_out:
if (rnp != rnp_root)
raw_spin_unlock(&rnp_root->lock);
return c;
}
/*
* Clean up any old requests for the just-ended grace period. Also return
* whether any additional grace periods have been requested. Also invoke
* rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads
* waiting for this grace period to complete.
*/
static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
{
int c = rnp->completed;
int needmore;
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
rcu_nocb_gp_cleanup(rsp, rnp);
rnp->need_future_gp[c & 0x1] = 0;
needmore = rnp->need_future_gp[(c + 1) & 0x1];
trace_rcu_future_gp(rnp, rdp, c, needmore ? "CleanupMore" : "Cleanup");
return needmore;
}
/*
* If there is room, assign a ->completed number to any callbacks on
* this CPU that have not already been assigned. Also accelerate any
......@@ -1129,6 +1249,8 @@ static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL];
rdp->nxtcompleted[i] = c;
}
/* Record any needed additional grace periods. */
rcu_start_future_gp(rnp, rdp);
/* Trace depending on how much we were able to accelerate. */
if (!*rdp->nxttail[RCU_WAIT_TAIL])
......@@ -1308,9 +1430,9 @@ static int rcu_gp_init(struct rcu_state *rsp)
rdp = this_cpu_ptr(rsp->rda);
rcu_preempt_check_blocked_tasks(rnp);
rnp->qsmask = rnp->qsmaskinit;
rnp->gpnum = rsp->gpnum;
ACCESS_ONCE(rnp->gpnum) = rsp->gpnum;
WARN_ON_ONCE(rnp->completed != rsp->completed);
rnp->completed = rsp->completed;
ACCESS_ONCE(rnp->completed) = rsp->completed;
if (rnp == rdp->mynode)
rcu_start_gp_per_cpu(rsp, rnp, rdp);
rcu_preempt_boost_start_gp(rnp);
......@@ -1319,7 +1441,8 @@ static int rcu_gp_init(struct rcu_state *rsp)
rnp->grphi, rnp->qsmask);
raw_spin_unlock_irq(&rnp->lock);
#ifdef CONFIG_PROVE_RCU_DELAY
if ((prandom_u32() % (rcu_num_nodes * 8)) == 0)
if ((prandom_u32() % (rcu_num_nodes * 8)) == 0 &&
system_state == SYSTEM_RUNNING)
schedule_timeout_uninterruptible(2);
#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
cond_resched();
......@@ -1361,6 +1484,7 @@ int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
static void rcu_gp_cleanup(struct rcu_state *rsp)
{
unsigned long gp_duration;
int nocb = 0;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
......@@ -1390,17 +1514,23 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
*/
rcu_for_each_node_breadth_first(rsp, rnp) {
raw_spin_lock_irq(&rnp->lock);
rnp->completed = rsp->gpnum;
ACCESS_ONCE(rnp->completed) = rsp->gpnum;
rdp = this_cpu_ptr(rsp->rda);
if (rnp == rdp->mynode)
__rcu_process_gp_end(rsp, rnp, rdp);
nocb += rcu_future_gp_cleanup(rsp, rnp);
raw_spin_unlock_irq(&rnp->lock);
cond_resched();
}
rnp = rcu_get_root(rsp);
raw_spin_lock_irq(&rnp->lock);
rcu_nocb_gp_set(rnp, nocb);
rsp->completed = rsp->gpnum; /* Declare grace period done. */
trace_rcu_grace_period(rsp->name, rsp->completed, "end");
rsp->fqs_state = RCU_GP_IDLE;
rdp = this_cpu_ptr(rsp->rda);
rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */
if (cpu_needs_another_gp(rsp, rdp))
rsp->gp_flags = 1;
raw_spin_unlock_irq(&rnp->lock);
......@@ -1476,57 +1606,62 @@ static int __noreturn rcu_gp_kthread(void *arg)
/*
* Start a new RCU grace period if warranted, re-initializing the hierarchy
* in preparation for detecting the next grace period. The caller must hold
* the root node's ->lock, which is released before return. Hard irqs must
* be disabled.
* the root node's ->lock and hard irqs must be disabled.
*
* Note that it is legal for a dying CPU (which is marked as offline) to
* invoke this function. This can happen when the dying CPU reports its
* quiescent state.
*/
static void
rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
__releases(rcu_get_root(rsp)->lock)
rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp)
{
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
struct rcu_node *rnp = rcu_get_root(rsp);
if (!rsp->gp_kthread ||
!cpu_needs_another_gp(rsp, rdp)) {
if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) {
/*
* Either we have not yet spawned the grace-period
* task, this CPU does not need another grace period,
* or a grace period is already in progress.
* Either way, don't start a new grace period.
*/
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
/*
* Because there is no grace period in progress right now,
* any callbacks we have up to this point will be satisfied
* by the next grace period. So this is a good place to
* assign a grace period number to recently posted callbacks.
*/
rcu_accelerate_cbs(rsp, rnp, rdp);
rsp->gp_flags = RCU_GP_FLAG_INIT;
raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
/* Ensure that CPU is aware of completion of last grace period. */
rcu_process_gp_end(rsp, rdp);
local_irq_restore(flags);
/* Wake up rcu_gp_kthread() to start the grace period. */
wake_up(&rsp->gp_wq);
}
/*
* Similar to rcu_start_gp_advanced(), but also advance the calling CPU's
* callbacks. Note that rcu_start_gp_advanced() cannot do this because it
* is invoked indirectly from rcu_advance_cbs(), which would result in
* endless recursion -- or would do so if it wasn't for the self-deadlock
* that is encountered beforehand.
*/
static void
rcu_start_gp(struct rcu_state *rsp)
{
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
struct rcu_node *rnp = rcu_get_root(rsp);
/*
* If there is no grace period in progress right now, any
* callbacks we have up to this point will be satisfied by the
* next grace period. Also, advancing the callbacks reduces the
* probability of false positives from cpu_needs_another_gp()
* resulting in pointless grace periods. So, advance callbacks
* then start the grace period!
*/
rcu_advance_cbs(rsp, rnp, rdp);
rcu_start_gp_advanced(rsp, rnp, rdp);
}
/*
* Report a full set of quiescent states to the specified rcu_state
* data structure. This involves cleaning up after the prior grace
* period and letting rcu_start_gp() start up the next grace period
* if one is needed. Note that the caller must hold rnp->lock, as
* required by rcu_start_gp(), which will release it.
* if one is needed. Note that the caller must hold rnp->lock, which
* is released before return.
*/
static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
__releases(rcu_get_root(rsp)->lock)
......@@ -2124,7 +2259,8 @@ __rcu_process_callbacks(struct rcu_state *rsp)
local_irq_save(flags);
if (cpu_needs_another_gp(rsp, rdp)) {
raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
rcu_start_gp(rsp, flags); /* releases above lock */
rcu_start_gp(rsp);
raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
} else {
local_irq_restore(flags);
}
......@@ -2169,7 +2305,8 @@ static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
static void invoke_rcu_core(void)
{
raise_softirq(RCU_SOFTIRQ);
if (cpu_online(smp_processor_id()))
raise_softirq(RCU_SOFTIRQ);
}
/*
......@@ -2204,11 +2341,11 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
/* Start a new grace period if one not already started. */
if (!rcu_gp_in_progress(rsp)) {
unsigned long nestflag;
struct rcu_node *rnp_root = rcu_get_root(rsp);
raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */
raw_spin_lock(&rnp_root->lock);
rcu_start_gp(rsp);
raw_spin_unlock(&rnp_root->lock);
} else {
/* Give the grace period a kick. */
rdp->blimit = LONG_MAX;
......@@ -2628,19 +2765,27 @@ static int rcu_pending(int cpu)
}
/*
* 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.
* Return true if the specified CPU has any callback. If all_lazy is
* non-NULL, store an indication of whether all callbacks are lazy.
* (If there are no callbacks, all of them are deemed to be lazy.)
*/
static int rcu_cpu_has_callbacks(int cpu)
static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
{
bool al = true;
bool hc = false;
struct rcu_data *rdp;
struct rcu_state *rsp;
/* RCU callbacks either ready or pending? */
for_each_rcu_flavor(rsp)
if (per_cpu_ptr(rsp->rda, cpu)->nxtlist)
return 1;
return 0;
for_each_rcu_flavor(rsp) {
rdp = per_cpu_ptr(rsp->rda, cpu);
if (rdp->qlen != rdp->qlen_lazy)
al = false;
if (rdp->nxtlist)
hc = true;
}
if (all_lazy)
*all_lazy = al;
return hc;
}
/*
......@@ -2859,7 +3004,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
atomic_set(&rdp->dynticks->dynticks,
(atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
rcu_prepare_for_idle_init(cpu);
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
/* Add CPU to rcu_node bitmasks. */
......@@ -2909,7 +3053,6 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
struct rcu_node *rnp = rdp->mynode;
struct rcu_state *rsp;
int ret = NOTIFY_OK;
trace_rcu_utilization("Start CPU hotplug");
switch (action) {
......@@ -2923,21 +3066,12 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
rcu_boost_kthread_setaffinity(rnp, -1);
break;
case CPU_DOWN_PREPARE:
if (nocb_cpu_expendable(cpu))
rcu_boost_kthread_setaffinity(rnp, cpu);
else
ret = NOTIFY_BAD;
rcu_boost_kthread_setaffinity(rnp, cpu);
break;
case CPU_DYING:
case CPU_DYING_FROZEN:
/*
* The whole machine is "stopped" except this CPU, so we can
* touch any data without introducing corruption. We send the
* dying CPU's callbacks to an arbitrarily chosen online CPU.
*/
for_each_rcu_flavor(rsp)
rcu_cleanup_dying_cpu(rsp);
rcu_cleanup_after_idle(cpu);
break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
......@@ -2950,7 +3084,7 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
break;
}
trace_rcu_utilization("End CPU hotplug");
return ret;
return NOTIFY_OK;
}
/*
......@@ -3085,6 +3219,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
}
rnp->level = i;
INIT_LIST_HEAD(&rnp->blkd_tasks);
rcu_init_one_nocb(rnp);
}
}
......@@ -3170,8 +3305,7 @@ void __init rcu_init(void)
rcu_init_one(&rcu_sched_state, &rcu_sched_data);
rcu_init_one(&rcu_bh_state, &rcu_bh_data);
__rcu_init_preempt();
rcu_init_nocb();
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
/*
* We don't need protection against CPU-hotplug here because
......
......@@ -88,18 +88,13 @@ struct rcu_dynticks {
int dynticks_nmi_nesting; /* Track NMI nesting level. */
atomic_t dynticks; /* Even value for idle, else odd. */
#ifdef CONFIG_RCU_FAST_NO_HZ
int dyntick_drain; /* Prepare-for-idle state variable. */
unsigned long dyntick_holdoff;
/* No retries for the jiffy of failure. */
struct timer_list idle_gp_timer;
/* Wake up CPU sleeping with callbacks. */
unsigned long idle_gp_timer_expires;
/* When to wake up CPU (for repost). */
bool idle_first_pass; /* First pass of attempt to go idle? */
bool all_lazy; /* Are all CPU's CBs lazy? */
unsigned long nonlazy_posted;
/* # times non-lazy CBs posted to CPU. */
unsigned long nonlazy_posted_snap;
/* idle-period nonlazy_posted snapshot. */
unsigned long last_accelerate;
/* Last jiffy CBs were accelerated. */
int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
};
......@@ -134,9 +129,6 @@ struct rcu_node {
/* elements that need to drain to allow the */
/* current expedited grace period to */
/* complete (only for TREE_PREEMPT_RCU). */
atomic_t wakemask; /* CPUs whose kthread needs to be awakened. */
/* Since this has meaning only for leaf */
/* rcu_node structures, 32 bits suffices. */
unsigned long qsmaskinit;
/* Per-GP initial value for qsmask & expmask. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
......@@ -196,6 +188,12 @@ struct rcu_node {
/* Refused to boost: not sure why, though. */
/* This can happen due to race conditions. */
#endif /* #ifdef CONFIG_RCU_BOOST */
#ifdef CONFIG_RCU_NOCB_CPU
wait_queue_head_t nocb_gp_wq[2];
/* Place for rcu_nocb_kthread() to wait GP. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
int need_future_gp[2];
/* Counts of upcoming no-CB GP requests. */
raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
} ____cacheline_internodealigned_in_smp;
......@@ -328,6 +326,11 @@ struct rcu_data {
struct task_struct *nocb_kthread;
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
/* 8) RCU CPU stall data. */
#ifdef CONFIG_RCU_CPU_STALL_INFO
unsigned int softirq_snap; /* Snapshot of softirq activity. */
#endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
int cpu;
struct rcu_state *rsp;
};
......@@ -375,12 +378,6 @@ struct rcu_state {
struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */
void (*call)(struct rcu_head *head, /* call_rcu() flavor. */
void (*func)(struct rcu_head *head));
#ifdef CONFIG_RCU_NOCB_CPU
void (*call_remote)(struct rcu_head *head,
void (*func)(struct rcu_head *head));
/* call_rcu() flavor, but for */
/* placing on remote CPU. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
/* The following fields are guarded by the root rcu_node's lock. */
......@@ -443,6 +440,7 @@ struct rcu_state {
unsigned long gp_max; /* Maximum GP duration in */
/* jiffies. */
char *name; /* Name of structure. */
char abbr; /* Abbreviated name. */
struct list_head flavors; /* List of RCU flavors. */
};
......@@ -520,7 +518,6 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
struct rcu_node *rnp);
#endif /* #ifdef CONFIG_RCU_BOOST */
static void __cpuinit rcu_prepare_kthreads(int cpu);
static void rcu_prepare_for_idle_init(int cpu);
static void rcu_cleanup_after_idle(int cpu);
static void rcu_prepare_for_idle(int cpu);
static void rcu_idle_count_callbacks_posted(void);
......@@ -529,16 +526,18 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
static void print_cpu_stall_info_end(void);
static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static void increment_cpu_stall_ticks(void);
static int rcu_nocb_needs_gp(struct rcu_state *rsp);
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp);
static void rcu_init_one_nocb(struct rcu_node *rnp);
static bool is_nocb_cpu(int cpu);
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
bool lazy);
static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
struct rcu_data *rdp);
static bool nocb_cpu_expendable(int cpu);
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
static void rcu_spawn_nocb_kthreads(struct rcu_state *rsp);
static void init_nocb_callback_list(struct rcu_data *rdp);
static void __init rcu_init_nocb(void);
static bool init_nocb_callback_list(struct rcu_data *rdp);
#endif /* #ifndef RCU_TREE_NONCORE */
......
此差异已折叠。
......@@ -46,8 +46,6 @@
#define RCU_TREE_NONCORE
#include "rcutree.h"
#define ulong2long(a) (*(long *)(&(a)))
static int r_open(struct inode *inode, struct file *file,
const struct seq_operations *op)
{
......
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