diff options
Diffstat (limited to 'debian/patches-rt/0006_sched_make_rcu_nest_depth_distinct_in___might_resched.patch')
| -rw-r--r-- | debian/patches-rt/0006_sched_make_rcu_nest_depth_distinct_in___might_resched.patch | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/debian/patches-rt/0006_sched_make_rcu_nest_depth_distinct_in___might_resched.patch b/debian/patches-rt/0006_sched_make_rcu_nest_depth_distinct_in___might_resched.patch new file mode 100644 index 000000000..1aa6fab12 --- /dev/null +++ b/debian/patches-rt/0006_sched_make_rcu_nest_depth_distinct_in___might_resched.patch @@ -0,0 +1,124 @@ +From: Thomas Gleixner <tglx@linutronix.de> +Subject: sched: Make RCU nest depth distinct in __might_resched() +Date: Thu, 23 Sep 2021 18:54:43 +0200 +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.15/older/patches-5.15.3-rt21.tar.xz + +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: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Link: https://lore.kernel.org/r/20210923165358.243232823@linutronix.de +--- + include/linux/kernel.h | 4 ++-- + include/linux/sched.h | 3 +++ + kernel/sched/core.c | 28 ++++++++++++++++------------ + 3 files changed, 21 insertions(+), 14 deletions(-) + +--- a/include/linux/kernel.h ++++ b/include/linux/kernel.h +@@ -111,7 +111,7 @@ static __always_inline void might_resche + #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 *f + # 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) +--- a/include/linux/sched.h ++++ b/include/linux/sched.h +@@ -2057,6 +2057,9 @@ extern int __cond_resched_lock(spinlock_ + extern int __cond_resched_rwlock_read(rwlock_t *lock); + extern int __cond_resched_rwlock_write(rwlock_t *lock); + ++#define MIGHT_RESCHED_RCU_SHIFT 8 ++#define MIGHT_RESCHED_PREEMPT_MASK ((1U << MIGHT_RESCHED_RCU_SHIFT) - 1) ++ + #define cond_resched_lock(lock) ({ \ + __might_resched(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET); \ + __cond_resched_lock(lock); \ +--- a/kernel/sched/core.c ++++ b/kernel/sched/core.c +@@ -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 + 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, i + /* 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, i + 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, i + 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); |