]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
signal: align __lock_task_sighand() irq disabling and RCU
authorPaul E. McKenney <paul.mckenney@linaro.org>
Tue, 19 Jul 2011 10:25:36 +0000 (03:25 -0700)
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Wed, 20 Jul 2011 18:04:54 +0000 (11:04 -0700)
commita841796f11c90d53dbac773be56b04fbee8af272
tree9401a53faddecc7c1644565d0e22630028f82bca
parentec433f0c51527426989ea8a38a856d810d739414
signal: align __lock_task_sighand() irq disabling and RCU

The __lock_task_sighand() function calls rcu_read_lock() with interrupts
and preemption enabled, but later calls rcu_read_unlock() with interrupts
disabled.  It is therefore possible that this RCU read-side critical
section will be preempted and later RCU priority boosted, which means that
rcu_read_unlock() will call rt_mutex_unlock() in order to deboost itself, but
with interrupts disabled. This results in lockdep splats, so this commit
nests the RCU read-side critical section within the interrupt-disabled
region of code.  This prevents the RCU read-side critical section from
being preempted, and thus prevents the attempt to deboost with interrupts
disabled.

It is quite possible that a better long-term fix is to make rt_mutex_unlock()
disable irqs when acquiring the rt_mutex structure's ->wait_lock.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
kernel/signal.c