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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-01-30 23:56:46 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-03-04 08:05:41 -0800 |
| commit | e611eecd6f9f91d74beda8cfbb3b5e02abdeb5a1 (patch) | |
| tree | e33c1874cf9cb737032a11985c537097625e28a1 /kernel/rcupdate.c | |
| parent | fe8e64071a4ff5925ced4f33cb32ba090a04649c (diff) | |
| download | lwn-e611eecd6f9f91d74beda8cfbb3b5e02abdeb5a1.tar.gz lwn-e611eecd6f9f91d74beda8cfbb3b5e02abdeb5a1.zip | |
rcu: add comment saying why DEBUG_OBJECTS_RCU_HEAD depends on PREEMPT.
The build will break if you change the Kconfig to allow
DEBUG_OBJECTS_RCU_HEAD and !PREEMPT, so document the reasoning
near where the breakage would occur.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcupdate.c')
| -rw-r--r-- | kernel/rcupdate.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index afd21d17c081..f3240e987928 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -214,6 +214,11 @@ static int rcuhead_fixup_free(void *addr, enum debug_obj_state state) * Ensure that queued callbacks are all executed. * If we detect that we are nested in a RCU read-side critical * section, we should simply fail, otherwise we would deadlock. + * Note that the machinery to reliably determine whether + * or not we are in an RCU read-side critical section + * exists only in the preemptible RCU implementations + * (TINY_PREEMPT_RCU and TREE_PREEMPT_RCU), which is why + * DEBUG_OBJECTS_RCU_HEAD is disallowed if !PREEMPT. */ if (rcu_preempt_depth() != 0 || preempt_count() != 0 || irqs_disabled()) { |