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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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28
kernel/sched/core.c
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@@ -9468,12 +9468,6 @@ void __init sched_init(void)
}
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
static inline int preempt_count_equals(int preempt_offset)
{
int nested = preempt_count() + rcu_preempt_depth();
return (nested == preempt_offset);
}
void __might_sleep(const char *file, int line)
{
@@ -9505,7 +9499,16 @@ static void print_preempt_disable_ip(int preempt_offset, unsigned long ip)
print_ip_sym(KERN_ERR, ip);
}
void __might_resched(const char *file, int line, int preempt_offset)
static inline bool resched_offsets_ok(unsigned int offsets)
{
unsigned int nested = preempt_count();
nested += rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT;
return nested == offsets;
}
void __might_resched(const char *file, int line, unsigned int offsets)
{
/* Ratelimiting timestamp: */
static unsigned long prev_jiffy;
@@ -9515,7 +9518,7 @@ void __might_resched(const char *file, int line, int preempt_offset)
/* WARN_ON_ONCE() by default, no rate limit required: */
rcu_sleep_check();
if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
if ((resched_offsets_ok(offsets) && !irqs_disabled() &&
!is_idle_task(current) && !current->non_block_count) ||
system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
oops_in_progress)
@@ -9534,11 +9537,11 @@ void __might_resched(const char *file, int line, int preempt_offset)
in_atomic(), irqs_disabled(), current->non_block_count,
current->pid, current->comm);
pr_err("preempt_count: %x, expected: %x\n", preempt_count(),
preempt_offset);
offsets & MIGHT_RESCHED_PREEMPT_MASK);
if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
pr_err("RCU nest depth: %d, expected: 0\n",
rcu_preempt_depth());
pr_err("RCU nest depth: %d, expected: %u\n",
rcu_preempt_depth(), offsets >> MIGHT_RESCHED_RCU_SHIFT);
}
if (task_stack_end_corrupted(current))
@@ -9548,7 +9551,8 @@ void __might_resched(const char *file, int line, int preempt_offset)
if (irqs_disabled())
print_irqtrace_events(current);
print_preempt_disable_ip(preempt_offset, preempt_disable_ip);
print_preempt_disable_ip(offsets & MIGHT_RESCHED_PREEMPT_MASK,
preempt_disable_ip);
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);