kernel/spinlock.c implements two versions of spinlock wrappers around
the arch-specific implementations:
1) A simple passthrough which implies disabled preemption while spinning
2) A "preemptible waiter" version which uses trylock.
Currently, PREEMPT && SMP will turn on the preemptible feature, and
lockdep or PREEMPT_RT will disable it. Disabling the feature for
lockdep makes perfect sense, but PREEMPT_RT is counter-intuitive. My
guess is that this was inadvertent, so this patch once again enables
the feature for PREEMPT_RT.
(Since PREEMPT is set for PREEMPT_RT, we simply get rid of the extra
condition).
I have tested the PREEMPT_RT kernel with this patch and all seems well.
Therefore, if there *is* an issue with running preemptible versions of
these spinlocks under PREEMPT_RT, it is not immediately apparent why.
Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
---
kernel/spinlock.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index c9bcf1b..b0e7f02 100644
--- a/kernel/spinlock.c
+++ b/kernel/spinlock.c
@@ -117,7 +117,7 @@ EXPORT_SYMBOL(__write_trylock_irqsave);
* not re-enabled during lock-acquire (which the preempt-spin-ops do):
*/
#if !defined(CONFIG_PREEMPT) || !defined(CONFIG_SMP) || \
- defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_PREEMPT_RT)
+ defined(CONFIG_DEBUG_LOCK_ALLOC)
void __lockfunc __read_lock(raw_rwlock_t *lock)
{
--
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