Messages in this thread Patch in this message | | | Date | Thu, 20 Oct 2022 12:33:57 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] tracing: Add trace_trigger kernel command line option |
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On Thu, 20 Oct 2022 08:59:00 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:
> On Wed, Oct 19, 2022 at 08:07:45PM -0400, Steven Rostedt wrote: > > On Wed, 19 Oct 2022 20:01:37 -0400 > > Steven Rostedt <rostedt@goodmis.org> wrote: > > > > > @@ -90,6 +90,10 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb) > > > #ifdef CONFIG_TRACEPOINTS > > > static inline void tracepoint_synchronize_unregister(void) > > > { > > > + /* Early updates do not need synchronization */ > > > + if (early_boot_irqs_disabled) > > > + return; > > > + > > > synchronize_srcu(&tracepoint_srcu); > > > synchronize_rcu(); > > > > I wonder if this check should be just moved to the RCU synchronization > > code? That is, if early_boot_irqs_disabled is set, do nothing, as there > > should be nothing to synchronize against. > > There already is a similar check, but it follows the lockdep check. > > Does the following patch help?
Not sure if it would.
I added this:
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index c03fd7037add..79ac31a6a87b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2748,9 +2748,12 @@ void trace_buffered_event_disable(void) disable_trace_buffered_event, NULL, 1); preempt_enable(); + if (!irqs_disabled()) + printk("IRQS DISABLED!! before %s:%d\n", __func__, __LINE__); /* Wait for all current users to finish */ - if (!early_boot_irqs_disabled) - synchronize_rcu(); + synchronize_rcu(); + if (!irqs_disabled()) + printk("IRQS DISABLED!! after %s:%d\n", __func__, __LINE__); for_each_tracing_cpu(cpu) { free_page((unsigned long)per_cpu(trace_buffered_event, cpu)); Which produced this:
[ 0.972867] ftrace: allocating 47021 entries in 184 pages [ 0.978285] ftrace section at ffffffffacef74c0 sorted properly [ 0.991153] ftrace: allocated 184 pages with 4 groups [ 0.996163] Dynamic Preempt: full [ 0.999354] rcu: Preemptible hierarchical RCU implementation. [ 1.005020] rcu: RCU restricting CPUs from NR_CPUS=128 to nr_cpu_ids=8. [ 1.011680] Tasks-RCU CPU stall warnings timeout set to 120000 (rcu_task_stall_timeout). [ 1.019813] Trampoline variant of Tasks RCU enabled. [ 1.024831] Rude variant of Tasks RCU enabled. [ 1.029330] Tracing variant of Tasks RCU enabled. [ 1.034089] rcu: RCU calculated value of scheduler-enlistment delay is 100 jiffies. [ 1.041699] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=8 [ 1.052607] IRQS DISABLED!! after trace_buffered_event_disable:2756 [ 1.058712] NR_IRQS: 8448, nr_irqs: 488, preallocated irqs: 16 [ 1.064670] NO_HZ: Full dynticks CPUs: 3. [ 1.068501] rcu: Offload RCU callbacks from CPUs: 3. [ 1.073519] rcu: srcu_init: Setting srcu_struct sizes based on contention. [ 1.080400] ------------[ cut here ]------------ [ 1.084938] Interrupts were enabled early [ 1.088919] WARNING: CPU: 0 PID: 0 at init/main.c:1061 start_kernel+0x36f/0x4e8 [ 1.096184] Modules linked in: [ 1.099213] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.1.0-rc1-test+ #468 [ 1.106047] Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 [ 1.114960] RIP: 0010:start_kernel+0x36f/0x4e8 [ 1.119373] Code: 48 27 53 e8 fd 7b 03 00 e8 55 72 e5 fe e8 6b 05 03 00 ff 15 2a f9 89 ff 0f ba e0 09 73 0e 48 c7 c7 98 25 31 ac e8 01 5b df fe <0f> 0b c6 05 c7 2c af ff 00 e8 ba 36 47 fe ff 15 14 f9 89 ff e8 56 [ 1.138057] RSP: 0000:ffffffffac603f30 EFLAGS: 00010286 [ 1.143248] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 1.150343] RDX: 0000000000000002 RSI: 00000000ffffdfff RDI: 0000000000000001 [ 1.157438] RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffffac603dd8 [ 1.164537] R10: 0000000000000003 R11: ffffffffac734168 R12: 000000000000180a [ 1.171633] R13: 00000000010fecf0 R14: 0000000000000000 R15: 00000000d44e3018 [ 1.178730] FS: 0000000000000000(0000) GS:ffff93ee1aa00000(0000) knlGS:0000000000000000 [ 1.186778] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.192489] CR2: ffff93ee1edff000 CR3: 000000002e60a001 CR4: 00000000000606f0 [ 1.199584] Call Trace: [ 1.202009] <TASK>
So I'm not sure how just updating srcu will do anything to prevent this.
-- Steve
> > Thanx, Paul > > ------------------------------------------------------------------------ > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > index ca4b5dcec675b..356ef70d5442c 100644 > --- a/kernel/rcu/srcutree.c > +++ b/kernel/rcu/srcutree.c > @@ -1267,14 +1267,15 @@ static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm) > { > struct rcu_synchronize rcu; > > + if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) > + return; > + > RCU_LOCKDEP_WARN(lockdep_is_held(ssp) || > lock_is_held(&rcu_bh_lock_map) || > lock_is_held(&rcu_lock_map) || > lock_is_held(&rcu_sched_lock_map), > "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section"); > > - if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) > - return; > might_sleep(); > check_init_srcu_struct(ssp); > init_completion(&rcu.completion);
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