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Date: Fri, 8 Jul 2022 16:21:58 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Mintu Patel <mintupatel89@...il.com>
Cc: badolevishal1116@...il.com, chinmoyghosh2001@...il.com,
linux-kernel@...r.kernel.org, mingo@...hat.com,
peterz@...radead.org, vimal.kumar32@...il.com, will@...nel.org
Subject: Re: [PATCH v2] rt_spin_lock: To list the correct owner of
rt_spin_lock
On Mon, 27 Jun 2022 21:41:38 +0530
Mintu Patel <mintupatel89@...il.com> wrote:
Hi Mintu,
FYI, a v2 should never be a reply to the v1. It should always start its own
thread, otherwise tooling and such will miss it.
> rt_spin_lock is actually mutex on RT Kernel so it goes for contention
> for lock. Currently owners of rt_spin_lock are decided before actual
> acquiring of lock. This patch would depict the correct owner of
> rt_spin_lock. The patch would help in solving crashes and deadlock
> due to race condition of lock
>
> acquiring rt_spin_lock acquired the lock released the lock
> <--------> <------->
> contention period Held period
>
> Thread1 Thread2
> _try_to_take_rt_mutex+0x95c+0x74 enqueue_task_dl+0x8cc/0x8dc
> rt_spin_lock_slowlock_locked+0xac+2 rt_mutex_setprio+0x28c/0x574
> rt_spin_lock_slowlock+0x5c/0x90 task_blocks_rt_mutex+0x240/0x310
> rt_spin_lock+0x58/0x5c rt_spin_lock_slowlock_locked+0xac/0x2
> driverA_acquire_lock+0x28/0x56 rt_spin_lock_slowlock+0x5c/0x90
> rt_spin_lock+0x58/0x5c
> driverB_acquire_lock+0x48/0x6c
>
> As per above call traces sample, Thread1 acquired the rt_spin_lock and
> went to critical section on the other hand Thread2 kept trying to acquire
> the same rt_spin_lock held by Thread1 ie contention period is too high.
> Finally Thread2 entered to dl queue due to high held time of the lock by
> Thread1. The below patch would help us to know the correct owner of
> rt_spin_lock and point us the driver's critical section. Respective
> driver need to be debugged for longer held period of lock.
>
> ex: cat /sys/kernel/debug/tracing/trace
>
> kworker/u13:0-150 [003] .....11 202.761025: rt_spinlock_acquire:
> Process: kworker/u13:0 is acquiring lock: &kbdev->hwaccess_lock
> kworker/u13:0-150 [003] .....11 202.761039: rt_spinlock_acquired:
> Process: kworker/u13:0 has acquired lock: &kbdev->hwaccess_lock
> kworker/u13:0-150 [003] .....11 202.761042: rt_spinlock_released:
> Process: kworker/u13:0 has released lock: &kbdev->hwaccess_lock
>
> Signed-off-by: Mintu Patel <mintupatel89@...il.com>
> Signed-off-by: Chinmoy Ghosh <chinmoyghosh2001@...il.com>
> Signed-off-by: Vishal Badole <badolevishal1116@...il.com>
> Signed-off-by: Vimal Kumar <vimal.kumar32@...il.com>
> ---
> include/trace/events/lock.h | 38 +++++++++++++++++++++++++++++++++
> kernel/locking/rtmutex.c | 4 ++++
> kernel/locking/rtmutex_common.h | 14 ++++++++++++
> 3 files changed, 56 insertions(+)
>
> diff --git a/include/trace/events/lock.h b/include/trace/events/lock.h
> index d7512129a324..0564474341c8 100644
> --- a/include/trace/events/lock.h
> +++ b/include/trace/events/lock.h
> @@ -36,6 +36,44 @@ TRACE_EVENT(lock_acquire,
> __get_str(name))
> );
>
> +DECLARE_EVENT_CLASS(rt_lock_class,
> +
> + TP_PROTO(struct lockdep_map *lock, struct task_struct *pname),
> +
> + TP_ARGS(lock, pname),
> +
> + TP_STRUCT__entry(
> + __string(name, lock->name)
> + __string(process_name, pname->comm)
> + ),
> +
> + TP_fast_assign(
> + __assign_str(name, lock->name);
> + __assign_str(process_name, pname->comm);
> + ),
> +
> + TP_printk("Process: %s is acquiring lock: %s", __get_str(process_name),
> + __get_str(name))
> +);
> +
> +DEFINE_EVENT(rt_lock_class, rt_spinlock_acquire,
> + TP_PROTO(struct lockdep_map *lock, struct task_struct *pname),
> + TP_ARGS(lock, pname));
> +
> +DEFINE_EVENT_PRINT(rt_lock_class, rt_spinlock_acquired,
> + TP_PROTO(struct lockdep_map *lock, struct task_struct *pname),
> + TP_ARGS(lock, pname),
> + TP_printk("Process: %s has acquired lock: %s", __get_str(process_name),
> + __get_str(name))
> + );
> +
> +DEFINE_EVENT_PRINT(rt_lock_class, rt_spinlock_released,
> + TP_PROTO(struct lockdep_map *lock, struct task_struct *pname),
> + TP_ARGS(lock, pname),
> + TP_printk("Process: %s has released lock: %s", __get_str(process_name),
> + __get_str(name))
> + );
> +
> DECLARE_EVENT_CLASS(lock,
>
> TP_PROTO(struct lockdep_map *lock, unsigned long ip),
> diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
> index 602eb7821a1b..80ba2c0d7923 100644
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -26,6 +26,7 @@
> #include <linux/timer.h>
> #include <linux/ww_mutex.h>
> #include <linux/blkdev.h>
> +#include <trace/events/lock.h>
>
> #include "rtmutex_common.h"
>
> @@ -1144,7 +1145,9 @@ void __lockfunc rt_spin_lock(spinlock_t *lock)
> rcu_read_lock();
> migrate_disable();
> spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
> + do_trace_rt_spinlock_acquire(lock, current);
> rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock);
> + do_trace_rt_spinlock_acquired(lock, current);
> }
> EXPORT_SYMBOL(rt_spin_lock);
>
> @@ -1169,6 +1172,7 @@ void __lockfunc rt_spin_unlock(spinlock_t *lock)
> {
> /* NOTE: we always pass in '1' for nested, for simplicity */
> spin_release(&lock->dep_map, 1, _RET_IP_);
> + do_trace_rt_spinlock_released(lock, current);
> rt_spin_lock_fastunlock(&lock->lock, rt_spin_lock_slowunlock);
> migrate_enable();
> rcu_read_unlock();
> diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h
> index 546aaf058b9e..185ffc1e7015 100644
> --- a/kernel/locking/rtmutex_common.h
> +++ b/kernel/locking/rtmutex_common.h
> @@ -25,6 +25,20 @@
> * @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree
> * @task: task reference to the blocked task
> */
> +
> +#ifdef CONFIG_RT_SPIN_LOCK_TRACING
> +#define do_trace_rt_spinlock_acquire(lock, task) \
> + trace_rt_spinlock_acquire(&lock->dep_map, task)
> +#define do_trace_rt_spinlock_acquired(lock, task) \
> + trace_rt_spinlock_acquired(&lock->dep_map, task)
> +#define do_trace_rt_spinlock_released(lock, task) \
> + trace_rt_spinlock_released(&lock->dep_map, task)
> +#else
> +#define do_trace_rt_spinlock_acquire(lock, task) do {} while(0)
> +#define do_trace_rt_spinlock_acquired(lock, task) do {} while(0)
> +#define do_trace_rt_spinlock_released(lock, task) do {} while(0)
> +#endif
> +
Acked-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Although it will need to be accepted by Peter Zijlstra.
-- Steve
> struct rt_mutex_waiter {
> struct rb_node tree_entry;
> struct rb_node pi_tree_entry;
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