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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-09-22 14:10:22 -0700 |
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committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2017-09-23 16:49:42 -0400 |
commit | 28585a832602747cbfa88ad8934013177a3aae38 (patch) | |
tree | 2308c7fd339e906bb13a296c998f5d3e52a39451 /kernel/extable.c | |
parent | 75df6e688ccd517e339a7c422ef7ad73045b18a2 (diff) |
rcu: Allow for page faults in NMI handlers
A number of architecture invoke rcu_irq_enter() on exception entry in
order to allow RCU read-side critical sections in the exception handler
when the exception is from an idle or nohz_full CPU. This works, at
least unless the exception happens in an NMI handler. In that case,
rcu_nmi_enter() would already have exited the extended quiescent state,
which would mean that rcu_irq_enter() would (incorrectly) cause RCU
to think that it is again in an extended quiescent state. This will
in turn result in lockdep splats in response to later RCU read-side
critical sections.
This commit therefore causes rcu_irq_enter() and rcu_irq_exit() to
take no action if there is an rcu_nmi_enter() in effect, thus avoiding
the unscheduled return to RCU quiescent state. This in turn should
make the kernel safe for on-demand RCU voyeurism.
Link: http://lkml.kernel.org/r/20170922211022.GA18084@linux.vnet.ibm.com
Cc: stable@vger.kernel.org
Fixes: 0be964be0 ("module: Sanitize RCU usage and locking")
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/extable.c')
0 files changed, 0 insertions, 0 deletions