* [PATCH rcu 1/2] rcu-tasks: Avoid pr_info() with spin lock in cblist_init_generic()
2023-05-10 17:10 [PATCH rcu 0/2] Tasks RCU updates for v6.5 Paul E. McKenney
@ 2023-05-10 17:10 ` Paul E. McKenney
2023-05-10 17:10 ` [PATCH rcu 2/2] rcu-tasks: Clarify the cblist_init_generic() function's pr_info() output Paul E. McKenney
1 sibling, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2023-05-10 17:10 UTC (permalink / raw)
To: rcu
Cc: linux-kernel, kernel-team, rostedt, Shigeru Yoshida, Zhang,
Qiang1, Paul E . McKenney
From: Shigeru Yoshida <syoshida@redhat.com>
pr_info() is called with rtp->cbs_gbl_lock spin lock locked. Because
pr_info() calls printk() that might sleep, this will result in BUG
like below:
[ 0.206455] cblist_init_generic: Setting adjustable number of callback queues.
[ 0.206463]
[ 0.206464] =============================
[ 0.206464] [ BUG: Invalid wait context ]
[ 0.206465] 5.19.0-00428-g9de1f9c8ca51 #5 Not tainted
[ 0.206466] -----------------------------
[ 0.206466] swapper/0/1 is trying to lock:
[ 0.206467] ffffffffa0167a58 (&port_lock_key){....}-{3:3}, at: serial8250_console_write+0x327/0x4a0
[ 0.206473] other info that might help us debug this:
[ 0.206473] context-{5:5}
[ 0.206474] 3 locks held by swapper/0/1:
[ 0.206474] #0: ffffffff9eb597e0 (rcu_tasks.cbs_gbl_lock){....}-{2:2}, at: cblist_init_generic.constprop.0+0x14/0x1f0
[ 0.206478] #1: ffffffff9eb579c0 (console_lock){+.+.}-{0:0}, at: _printk+0x63/0x7e
[ 0.206482] #2: ffffffff9ea77780 (console_owner){....}-{0:0}, at: console_emit_next_record.constprop.0+0x111/0x330
[ 0.206485] stack backtrace:
[ 0.206486] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.19.0-00428-g9de1f9c8ca51 #5
[ 0.206488] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.fc36 04/01/2014
[ 0.206489] Call Trace:
[ 0.206490] <TASK>
[ 0.206491] dump_stack_lvl+0x6a/0x9f
[ 0.206493] __lock_acquire.cold+0x2d7/0x2fe
[ 0.206496] ? stack_trace_save+0x46/0x70
[ 0.206497] lock_acquire+0xd1/0x2f0
[ 0.206499] ? serial8250_console_write+0x327/0x4a0
[ 0.206500] ? __lock_acquire+0x5c7/0x2720
[ 0.206502] _raw_spin_lock_irqsave+0x3d/0x90
[ 0.206504] ? serial8250_console_write+0x327/0x4a0
[ 0.206506] serial8250_console_write+0x327/0x4a0
[ 0.206508] console_emit_next_record.constprop.0+0x180/0x330
[ 0.206511] console_unlock+0xf7/0x1f0
[ 0.206512] vprintk_emit+0xf7/0x330
[ 0.206514] _printk+0x63/0x7e
[ 0.206516] cblist_init_generic.constprop.0.cold+0x24/0x32
[ 0.206518] rcu_init_tasks_generic+0x5/0xd9
[ 0.206522] kernel_init_freeable+0x15b/0x2a2
[ 0.206523] ? rest_init+0x160/0x160
[ 0.206526] kernel_init+0x11/0x120
[ 0.206527] ret_from_fork+0x1f/0x30
[ 0.206530] </TASK>
[ 0.207018] cblist_init_generic: Setting shift to 1 and lim to 1.
This patch moves pr_info() so that it is called without
rtp->cbs_gbl_lock locked.
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Tested-by: "Zhang, Qiang1" <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tasks.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 5f4fc8184dd0..65df1aaf0ce9 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -241,7 +241,6 @@ static void cblist_init_generic(struct rcu_tasks *rtp)
if (rcu_task_enqueue_lim < 0) {
rcu_task_enqueue_lim = 1;
rcu_task_cb_adjust = true;
- pr_info("%s: Setting adjustable number of callback queues.\n", __func__);
} else if (rcu_task_enqueue_lim == 0) {
rcu_task_enqueue_lim = 1;
}
@@ -272,6 +271,10 @@ static void cblist_init_generic(struct rcu_tasks *rtp)
raw_spin_unlock_rcu_node(rtpcp); // irqs remain disabled.
}
raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
+
+ if (rcu_task_cb_adjust)
+ pr_info("%s: Setting adjustable number of callback queues.\n", __func__);
+
pr_info("%s: Setting shift to %d and lim to %d.\n", __func__, data_race(rtp->percpu_enqueue_shift), data_race(rtp->percpu_enqueue_lim));
}
--
2.40.1
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH rcu 2/2] rcu-tasks: Clarify the cblist_init_generic() function's pr_info() output
2023-05-10 17:10 [PATCH rcu 0/2] Tasks RCU updates for v6.5 Paul E. McKenney
2023-05-10 17:10 ` [PATCH rcu 1/2] rcu-tasks: Avoid pr_info() with spin lock in cblist_init_generic() Paul E. McKenney
@ 2023-05-10 17:10 ` Paul E. McKenney
1 sibling, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2023-05-10 17:10 UTC (permalink / raw)
To: rcu; +Cc: linux-kernel, kernel-team, rostedt, Zqiang, Paul E . McKenney
From: Zqiang <qiang1.zhang@intel.com>
This commit uses rtp->name instead of __func__ and outputs the value
of rcu_task_cb_adjust, thus reducing console-log output.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tasks.h | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 65df1aaf0ce9..cf7b00af9474 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -272,10 +272,8 @@ static void cblist_init_generic(struct rcu_tasks *rtp)
}
raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
- if (rcu_task_cb_adjust)
- pr_info("%s: Setting adjustable number of callback queues.\n", __func__);
-
- pr_info("%s: Setting shift to %d and lim to %d.\n", __func__, data_race(rtp->percpu_enqueue_shift), data_race(rtp->percpu_enqueue_lim));
+ pr_info("%s: Setting shift to %d and lim to %d rcu_task_cb_adjust=%d.\n", rtp->name,
+ data_race(rtp->percpu_enqueue_shift), data_race(rtp->percpu_enqueue_lim), rcu_task_cb_adjust);
}
// IRQ-work handler that does deferred wakeup for call_rcu_tasks_generic().
--
2.40.1
^ permalink raw reply [flat|nested] 3+ messages in thread