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  1. 03 7月, 2008 11 次提交
  3. 02 7月, 2008 13 次提交
  5. 01 7月, 2008 8 次提交
    • G
      rcu: fix hotplug vs rcu race · 8558f8f8
      由 Gautham R Shenoy 提交于 
      Dhaval Giani reported this warning during cpu hotplug stress-tests:

| On running kernel compiles in parallel with cpu hotplug:
|
| WARNING: at arch/x86/kernel/smp.c:118
| native_smp_send_reschedule+0x21/0x36()
| Modules linked in:
| Pid: 27483, comm: cc1 Not tainted 2.6.26-rc7 #1
| [...]
|  [<c0110355>] native_smp_send_reschedule+0x21/0x36
|  [<c014fe8f>] force_quiescent_state+0x47/0x57
|  [<c014fef0>] call_rcu+0x51/0x6d
|  [<c01713b3>] __fput+0x130/0x158
|  [<c0171231>] fput+0x17/0x19
|  [<c016fd99>] filp_close+0x4d/0x57
|  [<c016fdff>] sys_close+0x5c/0x97

IMHO the warning is a spurious one.

cpu_online_map is updated by the _cpu_down() using stop_machine_run().
Since force_quiescent_state is invoked from irqs disabled section,
stop_machine_run() won't be executing while a cpu is executing
force_quiescent_state(). Hence the cpu_online_map is stable while we're
in the irq disabled section.

However, a cpu might have been offlined _just_ before we disabled irqs
while entering force_quiescent_state(). And rcu subsystem might not yet
have handled the CPU_DEAD notification, leading to the offlined cpu's
bit being set in the rcp->cpumask.

Hence cpumask = (rcp->cpumask & cpu_online_map) to prevent sending
smp_reschedule() to an offlined CPU.

Here's the timeline:

CPU_A						 CPU_B
--------------------------------------------------------------
cpu_down():					.
.					   	.
.						.
stop_machine(): /* disables preemption,		.
		 * and irqs */			.
.						.
.						.
take_cpu_down();				.
.						.
.						.
.						.
cpu_disable(); /*this removes cpu 		.
		*from cpu_online_map 		.
		*/				.
.						.
.						.
restart_machine(); /* enables irqs */		.
------WINDOW DURING WHICH rcp->cpumask is stale ---------------
.						call_rcu();
.						/* disables irqs here */
.						.force_quiescent_state();
.CPU_DEAD:					.for_each_cpu(rcp->cpumask)
.						.   smp_send_reschedule();
.						.
.						.   WARN_ON() for offlined CPU!
.
.
.
rcu_cpu_notify:
.
-------- WINDOW ENDS ------------------------------------------
rcu_offline_cpu() /* Which calls cpu_quiet()
		   * which removes
		   * cpu from rcp->cpumask.
		   */

If a new batch was started just before calling stop_machine_run(), the
"tobe-offlined" cpu is still present in rcp-cpumask.

During a cpu-offline, from take_cpu_down(), we queue an rt-prio idle
task as the next task to be picked by the scheduler. We also call
cpu_disable() which will disable any further interrupts and remove the
cpu's bit from the cpu_online_map.

Once the stop_machine_run() successfully calls take_cpu_down(), it calls
schedule(). That's the last time a schedule is called on the offlined
cpu, and hence the last time when rdp->passed_quiesc will be set to 1
through rcu_qsctr_inc().

But the cpu_quiet() will be on this cpu will be called only when the
next RCU_SOFTIRQ occurs on this CPU. So at this time, the offlined CPU
is still set in rcp->cpumask.

Now coming back to the idle_task which truely offlines the CPU, it does
check for a pending RCU and raises the softirq, since it will find
rdp->passed_quiesc to be 0 in this case. However, since the cpu is
offline I am not sure if the softirq will trigger on the CPU.

Even if it doesn't the rcu_offline_cpu() will find that rcp->completed
is not the same as rcp->cur, which means that our cpu could be holding
up the grace period progression. Hence we call cpu_quiet() and move
ahead.

But because of the window explained in the timeline, we could still have
a call_rcu() before the RCU subsystem executes it's CPU_DEAD
notification, and we send smp_send_reschedule() to offlined cpu while
trying to force the quiescent states. The appended patch adds comments
and prevents checking for offlined cpu everytime.

cpu_online_map is updated by the _cpu_down() using stop_machine_run().
Since force_quiescent_state is invoked from irqs disabled section,
stop_machine_run() won't be executing while a cpu is executing
force_quiescent_state(). Hence the cpu_online_map is stable while we're
in the irq disabled section.
Reported-by: NDhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: NGautham R Shenoy <ego@in.ibm.com>
Acked-by: NDhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rusty Russel <rusty@rustcorp.com.au>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      8558f8f8
    • T
      x86: fix NODES_SHIFT Kconfig range · efac4189
      由 Thomas Gleixner 提交于 
      commit 43238382
       x86: change size of node ids from u8 to s16

set the range for NODES_SHIFT to 1..15.

The possible range is 1..9

Fixes Bugzilla #10726
Reported-by: NDave Jones <davej@codemonkey.org.uk>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      efac4189
    • D
      Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/linville/wireless-2.6 · 2a64cc4b
      由 David S. Miller 提交于
      2a64cc4b
    • E
      mac80211: don't accept WEP keys other than WEP40 and WEP104 · 23976efe
      由 Emmanuel Grumbach 提交于 
      This patch makes mac80211 refuse a WEP key whose length is not WEP40 nor
WEP104.
Signed-off-by: NEmmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: NTomas Winkler <tomas.winkler@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>
      23976efe
    • P
      hostap: fix sparse warnings · 1bcca3c4
      由 Pavel Roskin 提交于 
      Rewrite AID calculation in handle_pspoll() to avoid truncating bits.
Make hostap_80211_header_parse() static, don't export it.  Avoid
shadowing variables.
Signed-off-by: NPavel Roskin <proski@gnu.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>
      1bcca3c4
    • P
      hostap: don't report useless WDS frames by default · 15ea0ebc
      由 Pavel Roskin 提交于 
      DEBUG_EXTRA is reported to the kernel log by default, but DEBUG_EXTRA2
is not.  Unrelated WDS frames pollute the log unnecessarily.
Signed-off-by: NPavel Roskin <proski@gnu.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>
      15ea0ebc
    • J
      textsearch: fix Boyer-Moore text search bug · aebb6a84
      由 Joonwoo Park 提交于 
      The current logic has a bug which cannot find matching pattern, if the
pattern is matched from the first character of target string.
for example:
	pattern=abc, string=abcdefg
	pattern=a,   string=abcdefg
Searching algorithm should return 0 for those things.
Signed-off-by: NJoonwoo Park <joonwpark81@gmail.com>
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      aebb6a84
    • J
      netfilter: nf_conntrack_tcp: fixing to check the lower bound of valid ACK · 84ebe1cd
      由 Jozsef Kadlecsik 提交于 
      Lost connections was reported by Thomas Bätzler (running 2.6.25 kernel) on
the netfilter mailing list (see the thread "Weird nat/conntrack Problem
with PASV FTP upload"). He provided tcpdump recordings which helped to
find a long lingering bug in conntrack.

In TCP connection tracking, checking the lower bound of valid ACK could
lead to mark valid packets as INVALID because:

 - We have got a "higher or equal" inequality, but the test checked
   the "higher" condition only; fixed.
 - If the packet contains a SACK option, it could occur that the ACK
   value was before the left edge of our (S)ACK "window": if a previous
   packet from the other party intersected the right edge of the window
   of the receiver, we could move forward the window parameters beyond
   accepting a valid ack. Therefore in this patch we check the rightmost
   SACK edge instead of the ACK value in the lower bound of valid (S)ACK
   test.
Signed-off-by: NJozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      84ebe1cd
  7. 30 6月, 2008 8 次提交