Commit ac8d513a authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

Merge branch 'master' into for-linus

parents bf992fa2 99bc4706
......@@ -82,6 +82,8 @@ block/
- info on the Block I/O (BIO) layer.
blockdev/
- info on block devices & drivers
btmrvl.txt
- info on Marvell Bluetooth driver usage.
cachetlb.txt
- describes the cache/TLB flushing interfaces Linux uses.
cdrom/
......
......@@ -743,3 +743,80 @@ Revised:
RCU, realtime RCU, sleepable RCU, performance.
"
}
@article{PaulEMcKenney2008RCUOSR
,author="Paul E. McKenney and Jonathan Walpole"
,title="Introducing technology into the {Linux} kernel: a case study"
,Year="2008"
,journal="SIGOPS Oper. Syst. Rev."
,volume="42"
,number="5"
,pages="4--17"
,issn="0163-5980"
,doi={http://doi.acm.org/10.1145/1400097.1400099}
,publisher="ACM"
,address="New York, NY, USA"
,annotation={
Linux changed RCU to a far greater degree than RCU has changed Linux.
}
}
@unpublished{PaulEMcKenney2008HierarchicalRCU
,Author="Paul E. McKenney"
,Title="Hierarchical {RCU}"
,month="November"
,day="3"
,year="2008"
,note="Available:
\url{http://lwn.net/Articles/305782/}
[Viewed November 6, 2008]"
,annotation="
RCU with combining-tree-based grace-period detection,
permitting it to handle thousands of CPUs.
"
}
@conference{PaulEMcKenney2009MaliciousURCU
,Author="Paul E. McKenney"
,Title="Using a Malicious User-Level {RCU} to Torture {RCU}-Based Algorithms"
,Booktitle="linux.conf.au 2009"
,month="January"
,year="2009"
,address="Hobart, Australia"
,note="Available:
\url{http://www.rdrop.com/users/paulmck/RCU/urcutorture.2009.01.22a.pdf}
[Viewed February 2, 2009]"
,annotation="
Realtime RCU and torture-testing RCU uses.
"
}
@unpublished{MathieuDesnoyers2009URCU
,Author="Mathieu Desnoyers"
,Title="[{RFC} git tree] Userspace {RCU} (urcu) for {Linux}"
,month="February"
,day="5"
,year="2009"
,note="Available:
\url{http://lkml.org/lkml/2009/2/5/572}
\url{git://lttng.org/userspace-rcu.git}
[Viewed February 20, 2009]"
,annotation="
Mathieu Desnoyers's user-space RCU implementation.
git://lttng.org/userspace-rcu.git
"
}
@unpublished{PaulEMcKenney2009BloatWatchRCU
,Author="Paul E. McKenney"
,Title="{RCU}: The {Bloatwatch} Edition"
,month="March"
,day="17"
,year="2009"
,note="Available:
\url{http://lwn.net/Articles/323929/}
[Viewed March 20, 2009]"
,annotation="
Uniprocessor assumptions allow simplified RCU implementation.
"
}
......@@ -2,14 +2,13 @@ RCU on Uniprocessor Systems
A common misconception is that, on UP systems, the call_rcu() primitive
may immediately invoke its function, and that the synchronize_rcu()
primitive may return immediately. The basis of this misconception
may immediately invoke its function. The basis of this misconception
is that since there is only one CPU, it should not be necessary to
wait for anything else to get done, since there are no other CPUs for
anything else to be happening on. Although this approach will -sort- -of-
work a surprising amount of the time, it is a very bad idea in general.
This document presents three examples that demonstrate exactly how bad an
idea this is.
This document presents three examples that demonstrate exactly how bad
an idea this is.
Example 1: softirq Suicide
......@@ -82,11 +81,18 @@ Quick Quiz #2: What locking restriction must RCU callbacks respect?
Summary
Permitting call_rcu() to immediately invoke its arguments or permitting
synchronize_rcu() to immediately return breaks RCU, even on a UP system.
So do not do it! Even on a UP system, the RCU infrastructure -must-
respect grace periods, and -must- invoke callbacks from a known environment
in which no locks are held.
Permitting call_rcu() to immediately invoke its arguments breaks RCU,
even on a UP system. So do not do it! Even on a UP system, the RCU
infrastructure -must- respect grace periods, and -must- invoke callbacks
from a known environment in which no locks are held.
It -is- safe for synchronize_sched() and synchronize_rcu_bh() to return
immediately on an UP system. It is also safe for synchronize_rcu()
to return immediately on UP systems, except when running preemptable
RCU.
Quick Quiz #3: Why can't synchronize_rcu() return immediately on
UP systems running preemptable RCU?
Answer to Quick Quiz #1:
......@@ -117,3 +123,13 @@ Answer to Quick Quiz #2:
callbacks acquire locks directly. However, a great many RCU
callbacks do acquire locks -indirectly-, for example, via
the kfree() primitive.
Answer to Quick Quiz #3:
Why can't synchronize_rcu() return immediately on UP systems
running preemptable RCU?
Because some other task might have been preempted in the middle
of an RCU read-side critical section. If synchronize_rcu()
simply immediately returned, it would prematurely signal the
end of the grace period, which would come as a nasty shock to
that other thread when it started running again.
......@@ -11,7 +11,10 @@ over a rather long period of time, but improvements are always welcome!
structure is updated more than about 10% of the time, then
you should strongly consider some other approach, unless
detailed performance measurements show that RCU is nonetheless
the right tool for the job.
the right tool for the job. Yes, you might think of RCU
as simply cutting overhead off of the readers and imposing it
on the writers. That is exactly why normal uses of RCU will
do much more reading than updating.
Another exception is where performance is not an issue, and RCU
provides a simpler implementation. An example of this situation
......@@ -240,10 +243,11 @@ over a rather long period of time, but improvements are always welcome!
instead need to use synchronize_irq() or synchronize_sched().
12. Any lock acquired by an RCU callback must be acquired elsewhere
with irq disabled, e.g., via spin_lock_irqsave(). Failing to
disable irq on a given acquisition of that lock will result in
deadlock as soon as the RCU callback happens to interrupt that
acquisition's critical section.
with softirq disabled, e.g., via spin_lock_irqsave(),
spin_lock_bh(), etc. Failing to disable irq on a given
acquisition of that lock will result in deadlock as soon as the
RCU callback happens to interrupt that acquisition's critical
section.
13. RCU callbacks can be and are executed in parallel. In many cases,
the callback code simply wrappers around kfree(), so that this
......@@ -310,3 +314,9 @@ over a rather long period of time, but improvements are always welcome!
Because these primitives only wait for pre-existing readers,
it is the caller's responsibility to guarantee safety to
any subsequent readers.
16. The various RCU read-side primitives do -not- contain memory
barriers. The CPU (and in some cases, the compiler) is free
to reorder code into and out of RCU read-side critical sections.
It is the responsibility of the RCU update-side primitives to
deal with this.
......@@ -36,7 +36,7 @@ o How can the updater tell when a grace period has completed
executed in user mode, or executed in the idle loop, we can
safely free up that item.
Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the
Preemptible variants of RCU (CONFIG_TREE_PREEMPT_RCU) get the
same effect, but require that the readers manipulate CPU-local
counters. These counters allow limited types of blocking
within RCU read-side critical sections. SRCU also uses
......@@ -79,10 +79,10 @@ o I hear that RCU is patented? What is with that?
o I hear that RCU needs work in order to support realtime kernels?
This work is largely completed. Realtime-friendly RCU can be
enabled via the CONFIG_PREEMPT_RCU kernel configuration parameter.
However, work is in progress for enabling priority boosting of
preempted RCU read-side critical sections. This is needed if you
have CPU-bound realtime threads.
enabled via the CONFIG_TREE_PREEMPT_RCU kernel configuration
parameter. However, work is in progress for enabling priority
boosting of preempted RCU read-side critical sections. This is
needed if you have CPU-bound realtime threads.
o Where can I find more information on RCU?
......
......@@ -170,6 +170,13 @@ module invokes call_rcu() from timers, you will need to first cancel all
the timers, and only then invoke rcu_barrier() to wait for any remaining
RCU callbacks to complete.
Of course, if you module uses call_rcu_bh(), you will need to invoke
rcu_barrier_bh() before unloading. Similarly, if your module uses
call_rcu_sched(), you will need to invoke rcu_barrier_sched() before
unloading. If your module uses call_rcu(), call_rcu_bh(), -and-
call_rcu_sched(), then you will need to invoke each of rcu_barrier(),
rcu_barrier_bh(), and rcu_barrier_sched().
Implementing rcu_barrier()
......
......@@ -76,8 +76,10 @@ torture_type The type of RCU to test: "rcu" for the rcu_read_lock() API,
"rcu_sync" for rcu_read_lock() with synchronous reclamation,
"rcu_bh" for the rcu_read_lock_bh() API, "rcu_bh_sync" for
rcu_read_lock_bh() with synchronous reclamation, "srcu" for
the "srcu_read_lock()" API, and "sched" for the use of
preempt_disable() together with synchronize_sched().
the "srcu_read_lock()" API, "sched" for the use of
preempt_disable() together with synchronize_sched(),
and "sched_expedited" for the use of preempt_disable()
with synchronize_sched_expedited().
verbose Enable debug printk()s. Default is disabled.
......@@ -162,6 +164,23 @@ of the "old" and "current" counters for the corresponding CPU. The
"idx" value maps the "old" and "current" values to the underlying array,
and is useful for debugging.
Similarly, sched_expedited RCU provides the following:
sched_expedited-torture: rtc: d0000000016c1880 ver: 1090796 tfle: 0 rta: 1090796 rtaf: 0 rtf: 1090787 rtmbe: 0 nt: 27713319
sched_expedited-torture: Reader Pipe: 12660320201 95875 0 0 0 0 0 0 0 0 0
sched_expedited-torture: Reader Batch: 12660424885 0 0 0 0 0 0 0 0 0 0
sched_expedited-torture: Free-Block Circulation: 1090795 1090795 1090794 1090793 1090792 1090791 1090790 1090789 1090788 1090787 0
state: -1 / 0:0 3:0 4:0
As before, the first four lines are similar to those for RCU.
The last line shows the task-migration state. The first number is
-1 if synchronize_sched_expedited() is idle, -2 if in the process of
posting wakeups to the migration kthreads, and N when waiting on CPU N.
Each of the colon-separated fields following the "/" is a CPU:state pair.
Valid states are "0" for idle, "1" for waiting for quiescent state,
"2" for passed through quiescent state, and "3" when a race with a
CPU-hotplug event forces use of the synchronize_sched() primitive.
USAGE
......
......@@ -191,8 +191,7 @@ rcu/rcuhier (which displays the struct rcu_node hierarchy).
The output of "cat rcu/rcudata" looks as follows:
rcu:
rcu:
rcu_sched:
0 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=10951/1 dn=0 df=1101 of=0 ri=36 ql=0 b=10
1 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=16117/1 dn=0 df=1015 of=0 ri=0 ql=0 b=10
2 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=1445/1 dn=0 df=1839 of=0 ri=0 ql=0 b=10
......@@ -306,7 +305,7 @@ comma-separated-variable spreadsheet format.
The output of "cat rcu/rcugp" looks as follows:
rcu: completed=33062 gpnum=33063
rcu_sched: completed=33062 gpnum=33063
rcu_bh: completed=464 gpnum=464
Again, this output is for both "rcu" and "rcu_bh". The fields are
......@@ -413,7 +412,7 @@ o Each element of the form "1/1 0:127 ^0" represents one struct
The output of "cat rcu/rcu_pending" looks as follows:
rcu:
rcu_sched:
0 np=255892 qsp=53936 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741
1 np=261224 qsp=54638 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792
2 np=237496 qsp=49664 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629
......
......@@ -136,10 +136,10 @@ rcu_read_lock()
Used by a reader to inform the reclaimer that the reader is
entering an RCU read-side critical section. It is illegal
to block while in an RCU read-side critical section, though
kernels built with CONFIG_PREEMPT_RCU can preempt RCU read-side
critical sections. Any RCU-protected data structure accessed
during an RCU read-side critical section is guaranteed to remain
unreclaimed for the full duration of that critical section.
kernels built with CONFIG_TREE_PREEMPT_RCU can preempt RCU
read-side critical sections. Any RCU-protected data structure
accessed during an RCU read-side critical section is guaranteed to
remain unreclaimed for the full duration of that critical section.
Reference counts may be used in conjunction with RCU to maintain
longer-term references to data structures.
......@@ -785,6 +785,7 @@ RCU pointer/list traversal:
rcu_dereference
list_for_each_entry_rcu
hlist_for_each_entry_rcu
hlist_nulls_for_each_entry_rcu
list_for_each_continue_rcu (to be deprecated in favor of new
list_for_each_entry_continue_rcu)
......@@ -807,19 +808,23 @@ RCU: Critical sections Grace period Barrier
rcu_read_lock synchronize_net rcu_barrier
rcu_read_unlock synchronize_rcu
synchronize_rcu_expedited
call_rcu
bh: Critical sections Grace period Barrier
rcu_read_lock_bh call_rcu_bh rcu_barrier_bh
rcu_read_unlock_bh
rcu_read_unlock_bh synchronize_rcu_bh
synchronize_rcu_bh_expedited
sched: Critical sections Grace period Barrier
[preempt_disable] synchronize_sched rcu_barrier_sched
[and friends] call_rcu_sched
rcu_read_lock_sched synchronize_sched rcu_barrier_sched
rcu_read_unlock_sched call_rcu_sched
[preempt_disable] synchronize_sched_expedited
[and friends]
SRCU: Critical sections Grace period Barrier
......@@ -827,6 +832,9 @@ SRCU: Critical sections Grace period Barrier
srcu_read_lock synchronize_srcu N/A
srcu_read_unlock
SRCU: Initialization/cleanup
init_srcu_struct
cleanup_srcu_struct
See the comment headers in the source code (or the docbook generated
from them) for more information.
......
=======================================================================
README for btmrvl driver
=======================================================================
All commands are used via debugfs interface.
=====================
Set/get driver configurations:
Path: /debug/btmrvl/config/
gpiogap=[n]
hscfgcmd
These commands are used to configure the host sleep parameters.
bit 8:0 -- Gap
bit 16:8 -- GPIO
where GPIO is the pin number of GPIO used to wake up the host.
It could be any valid GPIO pin# (e.g. 0-7) or 0xff (SDIO interface
wakeup will be used instead).
where Gap is the gap in milli seconds between wakeup signal and
wakeup event, or 0xff for special host sleep setting.
Usage:
# Use SDIO interface to wake up the host and set GAP to 0x80:
echo 0xff80 > /debug/btmrvl/config/gpiogap
echo 1 > /debug/btmrvl/config/hscfgcmd
# Use GPIO pin #3 to wake up the host and set GAP to 0xff:
echo 0x03ff > /debug/btmrvl/config/gpiogap
echo 1 > /debug/btmrvl/config/hscfgcmd
psmode=[n]
pscmd
These commands are used to enable/disable auto sleep mode
where the option is:
1 -- Enable auto sleep mode
0 -- Disable auto sleep mode
Usage:
# Enable auto sleep mode
echo 1 > /debug/btmrvl/config/psmode
echo 1 > /debug/btmrvl/config/pscmd
# Disable auto sleep mode
echo 0 > /debug/btmrvl/config/psmode
echo 1 > /debug/btmrvl/config/pscmd
hsmode=[n]
hscmd
These commands are used to enable host sleep or wake up firmware
where the option is:
1 -- Enable host sleep
0 -- Wake up firmware
Usage:
# Enable host sleep
echo 1 > /debug/btmrvl/config/hsmode
echo 1 > /debug/btmrvl/config/hscmd
# Wake up firmware
echo 0 > /debug/btmrvl/config/hsmode
echo 1 > /debug/btmrvl/config/hscmd
======================
Get driver status:
Path: /debug/btmrvl/status/
Usage:
cat /debug/btmrvl/status/<args>
where the args are:
curpsmode
This command displays current auto sleep status.
psstate
This command display the power save state.
hsstate
This command display the host sleep state.
txdnldrdy
This command displays the value of Tx download ready flag.
=====================
Use hcitool to issue raw hci command, refer to hcitool manual
Usage: Hcitool cmd <ogf> <ocf> [Parameters]
Interface Control Command
hcitool cmd 0x3f 0x5b 0xf5 0x01 0x00 --Enable All interface
hcitool cmd 0x3f 0x5b 0xf5 0x01 0x01 --Enable Wlan interface
hcitool cmd 0x3f 0x5b 0xf5 0x01 0x02 --Enable BT interface
hcitool cmd 0x3f 0x5b 0xf5 0x00 0x00 --Disable All interface
hcitool cmd 0x3f 0x5b 0xf5 0x00 0x01 --Disable Wlan interface
hcitool cmd 0x3f 0x5b 0xf5 0x00 0x02 --Disable BT interface
=======================================================================
SD8688 firmware:
/lib/firmware/sd8688_helper.bin
/lib/firmware/sd8688.bin
The images can be downloaded from:
git.infradead.org/users/dwmw2/linux-firmware.git/libertas/
......@@ -9,3 +9,8 @@ hostprogs-y := ucon
always := $(hostprogs-y)
HOSTCFLAGS_ucon.o += -I$(objtree)/usr/include
all: modules
modules clean:
$(MAKE) -C ../.. SUBDIRS=$(PWD) $@
......@@ -19,6 +19,8 @@
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#define pr_fmt(fmt) "cn_test: " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
......@@ -27,18 +29,17 @@
#include <linux/connector.h>
static struct cb_id cn_test_id = { 0x123, 0x456 };
static struct cb_id cn_test_id = { CN_NETLINK_USERS + 3, 0x456 };
static char cn_test_name[] = "cn_test";
static struct sock *nls;
static struct timer_list cn_test_timer;
void cn_test_callback(void *data)
static void cn_test_callback(struct cn_msg *msg)
{
struct cn_msg *msg = (struct cn_msg *)data;
printk("%s: %lu: idx=%x, val=%x, seq=%u, ack=%u, len=%d: %s.\n",
__func__, jiffies, msg->id.idx, msg->id.val,
msg->seq, msg->ack, msg->len, (char *)msg->data);
pr_info("%s: %lu: idx=%x, val=%x, seq=%u, ack=%u, len=%d: %s.\n",
__func__, jiffies, msg->id.idx, msg->id.val,
msg->seq, msg->ack, msg->len,
msg->len ? (char *)msg->data : "");
}
/*
......@@ -63,9 +64,7 @@ static int cn_test_want_notify(void)
skb = alloc_skb(size, GFP_ATOMIC);
if (!skb) {
printk(KERN_ERR "Failed to allocate new skb with size=%u.\n",
size);
pr_err("failed to allocate new skb with size=%u\n", size);
return -ENOMEM;
}
......@@ -114,12 +113,12 @@ static int cn_test_want_notify(void)
//netlink_broadcast(nls, skb, 0, ctl->group, GFP_ATOMIC);
netlink_unicast(nls, skb, 0, 0);
printk(KERN_INFO "Request was sent. Group=0x%x.\n", ctl->group);
pr_info("request was sent: group=0x%x\n", ctl->group);
return 0;
nlmsg_failure:
printk(KERN_ERR "Failed to send %u.%u\n", msg->seq, msg->ack);
pr_err("failed to send %u.%u\n", msg->seq, msg->ack);
kfree_skb(skb);
return -EINVAL;
}
......@@ -131,6 +130,8 @@ static void cn_test_timer_func(unsigned long __data)
struct cn_msg *m;
char data[32];
pr_debug("%s: timer fired with data %lu\n", __func__, __data);
m = kzalloc(sizeof(*m) + sizeof(data), GFP_ATOMIC);
if (m) {
......@@ -150,7 +151,7 @@ static void cn_test_timer_func(unsigned long __data)
cn_test_timer_counter++;
mod_timer(&cn_test_timer, jiffies + HZ);
mod_timer(&cn_test_timer, jiffies + msecs_to_jiffies(1000));
}
static int cn_test_init(void)
......@@ -168,8 +169,10 @@ static int cn_test_init(void)
}
setup_timer(&cn_test_timer, cn_test_timer_func, 0);
cn_test_timer.expires = jiffies + HZ;
add_timer(&cn_test_timer);
mod_timer(&cn_test_timer, jiffies + msecs_to_jiffies(1000));
pr_info("initialized with id={%u.%u}\n",
cn_test_id.idx, cn_test_id.val);
return 0;
......
......@@ -5,10 +5,10 @@ Kernel Connector.
Kernel connector - new netlink based userspace <-> kernel space easy
to use communication module.
Connector driver adds possibility to connect various agents using
netlink based network. One must register callback and
identifier. When driver receives special netlink message with
appropriate identifier, appropriate callback will be called.
The Connector driver makes it easy to connect various agents using a
netlink based network. One must register a callback and an identifier.
When the driver receives a special netlink message with the appropriate
identifier, the appropriate callback will be called.
From the userspace point of view it's quite straightforward:
......@@ -17,10 +17,10 @@ From the userspace point of view it's quite straightforward:
send();
recv();
But if kernelspace want to use full power of such connections, driver
writer must create special sockets, must know about struct sk_buff
handling... Connector allows any kernelspace agents to use netlink
based networking for inter-process communication in a significantly
But if kernelspace wants to use the full power of such connections, the
driver writer must create special sockets, must know about struct sk_buff
handling, etc... The Connector driver allows any kernelspace agents to use
netlink based networking for inter-process communication in a significantly
easier way:
int cn_add_callback(struct cb_id *id, char *name, void (*callback) (void *));
......@@ -32,15 +32,15 @@ struct cb_id
__u32 val;
};
idx and val are unique identifiers which must be registered in
connector.h for in-kernel usage. void (*callback) (void *) - is a
callback function which will be called when message with above idx.val
will be received by connector core. Argument for that function must
idx and val are unique identifiers which must be registered in the
connector.h header for in-kernel usage. void (*callback) (void *) is a
callback function which will be called when a message with above idx.val
is received by the connector core. The argument for that function must
be dereferenced to struct cn_msg *.
struct cn_msg
{
struct cb_id id;
struct cb_id id;
__u32 seq;
__u32 ack;
......@@ -55,92 +55,95 @@ Connector interfaces.
int cn_add_callback(struct cb_id *id, char *name, void (*callback) (void *));
Registers new callback with connector core.
Registers new callback with connector core.
struct cb_id *id - unique connector's user identifier.
It must be registered in connector.h for legal in-kernel users.
char *name - connector's callback symbolic name.
void (*callback) (void *) - connector's callback.
struct cb_id *id - unique connector's user identifier.
It must be registered in connector.h for legal in-kernel users.
char *name - connector's callback symbolic name.
void (*callback) (void *) - connector's callback.
Argument must be dereferenced to struct cn_msg *.
void cn_del_callback(struct cb_id *id);
Unregisters new callback with connector core.
Unregisters new callback with connector core.