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sched: Make RCU nest depth distinct in __might_resched()

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For !RT kernels RCU nest depth in __might_resched() is always expected to
be 0, but on RT kernels it can be non zero while the preempt count is
expected to be always 0.

Instead of playing magic games in interpreting the 'preempt_offset'
argument, rename it to 'offsets' and use the lower 8 bits for the expected
preempt count, allow to hand in the expected RCU nest depth in the upper
bits and adopt the __might_resched() code and related checks and printks.

The affected call sites are updated in subsequent steps.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.243232823@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-09-23 18:54:43 +02:00 • committed by Peter Zijlstra
parent 8d713b699e
commit 50e081b96e
3 changed files with 21 additions and 14 deletions
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4
include/linux/kernel.h
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@ -111,7 +111,7 @@ static __always_inline void might_resched(void)
#endif /* CONFIG_PREEMPT_* */
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
extern void __might_resched(const char *file, int line, int preempt_offset);
extern void __might_resched(const char *file, int line, unsigned int offsets);
extern void __might_sleep(const char *file, int line);
extern void __cant_sleep(const char *file, int line, int preempt_offset);
extern void __cant_migrate(const char *file, int line);
@ -169,7 +169,7 @@ extern void __cant_migrate(const char *file, int line);
# define non_block_end() WARN_ON(current->non_block_count-- == 0)
#else
static inline void __might_resched(const char *file, int line,
int preempt_offset) { }
unsigned int offsets) { }
static inline void __might_sleep(const char *file, int line) { }
# define might_sleep() do { might_resched(); } while (0)
# define cant_sleep() do { } while (0)