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Date: Mon, 29 Sep 2014 11:19:30 -0400
From: Sasha Levin <sasha.levin@...cle.com>
To: mingo@...nel.org
Cc: torvalds@...ux-foundation.org, paulmck@...ux.vnet.ibm.com,
peterz@...radead.org, ktkhai@...allels.com,
linux-kernel@...r.kernel.org, Sasha Levin <sasha.levin@...cle.com>
Subject: [PATCH] sched: Use RCU read lock on all calls to dl_bw_of()
Commit "sched: Use dl_bw_of() under RCU read lock" has missed a call
to dl_bw_of(), which has now started showing warnings:
[ 820.960972] ===============================
[ 820.961663] [ INFO: suspicious RCU usage. ]
[ 820.962344] 3.17.0-rc6-next-20140926-sasha-00051-g9253dff-dirty #1242 Not tainted
[ 820.963670] -------------------------------
[ 820.964454] kernel/sched/core.c:2008 sched RCU must be held!
[ 820.975556]
[ 820.975556] other info that might help us debug this:
[ 820.975556]
[ 820.987512] rcu_scheduler_active = 1, debug_locks = 1
[ 820.988546] 9 locks held by trinity-c157/26236:
[ 820.989274] #0: (&f->f_pos_lock){+.+.+.}, at: __fdget_pos (fs/file.c:718)
[ 820.994630] #1: (sb_writers#5){.+.+.+}, at: do_readv_writev (include/linux/fs.h:2270 fs/read_write.c:832)
[ 820.996170] #2: (&of->mutex){+.+.+.}, at: kernfs_fop_write (fs/kernfs/file.c:296)
[ 821.001816] #3: (s_active#23){.+.+.+}, at: kernfs_fop_write (fs/kernfs/file.c:296)
[ 821.003235] #4: (device_hotplug_lock){+.+.+.}, at: lock_device_hotplug_sysfs (drivers/base/core.c:66)
[ 821.004842] #5: (&dev->mutex){......}, at: device_offline (include/linux/device.h:900 drivers/base/core.c:1423)
[ 821.010610] #6: (cpu_add_remove_lock){+.+.+.}, at: cpu_down (kernel/cpu.c:426)
[ 821.011859] #7: (cpu_hotplug.lock){++++++}, at: cpu_hotplug_begin (kernel/cpu.c:152)
[ 821.013208] #8: (cpu_hotplug.lock#2){+.+.+.}, at: cpu_hotplug_begin (kernel/cpu.c:158)
[ 821.027101]
[ 821.027101] stack backtrace:
[ 821.027903] CPU: 17 PID: 26236 Comm: trinity-c157 Not tainted 3.17.0-rc6-next-20140926-sasha-00051-g9253dff-dirty #1242
[ 821.030246] 0000000000000001 0000000000000000 0000000000000001 ffff880803363a98
[ 821.038543] ffffffffb5f0070f 0000000000000011 ffff8808271eb000 ffff880803363ac8
[ 821.039967] ffffffffb124e8ed 0000000000000000 ffff880803363bbc 0000000000000013
[ 821.041455] Call Trace:
[ 821.042038] dump_stack (lib/dump_stack.c:52)
[ 821.043005] lockdep_rcu_suspicious (kernel/locking/lockdep.c:4265)
[ 821.044169] sched_cpu_inactive (kernel/sched/core.c:2008 kernel/sched/core.c:5271)
[ 821.050486] notifier_call_chain (kernel/notifier.c:93)
[ 821.051594] __raw_notifier_call_chain (kernel/notifier.c:395)
[ 821.052766] _cpu_down (include/linux/notifier.h:179 kernel/cpu.c:219 kernel/cpu.c:356)
[ 821.053809] ? cpu_down (kernel/cpu.c:426)
[ 821.054770] cpu_down (kernel/cpu.c:431)
[ 821.062497] cpu_subsys_offline (drivers/base/cpu.c:69)
[ 821.063500] device_offline (drivers/base/core.c:1428)
[ 821.064428] ? cpu_device_release (drivers/base/cpu.c:67)
[ 821.065429] online_store (drivers/base/core.c:451 (discriminator 2))
[ 821.066390] dev_attr_store (drivers/base/core.c:138)
[ 821.067328] ? dev_driver_string (drivers/base/core.c:130)
[ 821.073698] sysfs_kf_write (fs/sysfs/file.c:116)
[ 821.074496] ? sysfs_file_ops (fs/sysfs/file.c:108)
[ 821.075312] kernfs_fop_write (fs/kernfs/file.c:308)
[ 821.076135] ? do_readv_writev (include/linux/fs.h:2270 fs/read_write.c:832)
[ 821.076999] do_loop_readv_writev (fs/read_write.c:710)
[ 821.078066] ? kernfs_vma_page_mkwrite (fs/kernfs/file.c:267)
[ 821.079252] do_readv_writev (fs/read_write.c:842)
[ 821.080495] ? kernfs_vma_page_mkwrite (fs/kernfs/file.c:267)
[ 821.081644] ? mutex_lock_nested (./arch/x86/include/asm/preempt.h:98 kernel/locking/mutex.c:599 kernel/locking/mutex.c:616)
[ 821.086535] ? __fdget_pos (fs/file.c:718)
[ 821.087447] ? __fdget_pos (fs/file.c:718)
[ 821.088363] ? rcu_read_lock_held (kernel/rcu/update.c:169)
[ 821.089425] vfs_writev (fs/read_write.c:881)
[ 821.090486] SyS_writev (fs/read_write.c:913 fs/read_write.c:905)
[ 821.091382] tracesys_phase2 (arch/x86/kernel/entry_64.S:529)
Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
---
kernel/sched/core.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e6cfd9b..91bfbbb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5261,6 +5261,9 @@ static int sched_cpu_inactive(struct notifier_block *nfb,
{
unsigned long flags;
long cpu = (long)hcpu;
+ int ret;
+
+ rcu_read_lock();
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
@@ -5277,13 +5280,19 @@ static int sched_cpu_inactive(struct notifier_block *nfb,
overflow = __dl_overflow(dl_b, cpus, 0, 0);
raw_spin_unlock_irqrestore(&dl_b->lock, flags);
+ ret = notifier_from_errno(-EBUSY);
if (overflow)
- return notifier_from_errno(-EBUSY);
+ goto done;
}
- return NOTIFY_OK;
+ ret = NOTIFY_OK;
+ goto done;
}
- return NOTIFY_DONE;
+ ret = NOTIFY_DONE;
+
+done:
+ rcu_read_unlock();
+ return ret;
}
static int __init migration_init(void)
--
1.7.10.4
--
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