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| author | Thomas Gleixner <tglx@linutronix.de> | 2021-09-23 18:54:44 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-10-01 13:57:51 +0200 |
| commit | 3e9cc688e56cc2abb9b6067f57c8397f6c96d42c (patch) | |
| tree | 71b840a99263940d42c5d3fbe357f42817e83813 /include/linux/preempt.h | |
| parent | 50e081b96e35e43b65591f40f7376204decd1cb5 (diff) | |
| download | linux-3e9cc688e56cc2abb9b6067f57c8397f6c96d42c.tar.gz linux-3e9cc688e56cc2abb9b6067f57c8397f6c96d42c.tar.bz2 linux-3e9cc688e56cc2abb9b6067f57c8397f6c96d42c.zip | |
sched: Make cond_resched_lock() variants RT aware
The __might_resched() checks in the cond_resched_lock() variants use
PREEMPT_LOCK_OFFSET for preempt count offset checking which takes the
preemption disable by the spin_lock() which is still held at that point
into account.
On PREEMPT_RT enabled kernels spin/rw_lock held sections stay preemptible
which means PREEMPT_LOCK_OFFSET is 0, but that still triggers the
__might_resched() check because that takes RCU read side nesting into
account.
On RT enabled kernels spin/read/write_lock() issue rcu_read_lock() to
resemble the !RT semantics, which means in cond_resched_lock() the might
resched check will see preempt_count() == 0 and rcu_preempt_depth() == 1.
Introduce PREEMPT_LOCK_SCHED_OFFSET for those might resched checks and map
them depending on CONFIG_PREEMPT_RT.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.305969211@linutronix.de
Diffstat (limited to 'include/linux/preempt.h')
| -rw-r--r-- | include/linux/preempt.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 4d244e295e85..031898b38d06 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -122,9 +122,10 @@ * The preempt_count offset after spin_lock() */ #if !defined(CONFIG_PREEMPT_RT) -#define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET +#define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET #else -#define PREEMPT_LOCK_OFFSET 0 +/* Locks on RT do not disable preemption */ +#define PREEMPT_LOCK_OFFSET 0 #endif /* |