From b96285e10aad234acfa0628f7e8336990f778c03 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Mon, 28 Jun 2021 11:49:53 -0400 Subject: [PATCH] tracing: Have osnoise_main() add a quiescent state for task rcu ftracetest triggered: INFO: rcu_tasks detected stalls on tasks: 00000000b92b832d: .. nvcsw: 1/1 holdout: 1 idle_cpu: -1/7 task:osnoise/7 state:R running task stack: 0 pid: 2133 ppid: 2 flags:0x00004000 Call Trace: ? asm_sysvec_apic_timer_interrupt+0x12/0x20 ? asm_sysvec_apic_timer_interrupt+0x12/0x20 ? trace_hardirqs_on+0x2b/0xe0 ? asm_sysvec_apic_timer_interrupt+0x12/0x20 ? trace_clock_local+0xc/0x20 ? osnoise_main+0x10e/0x450 ? trace_softirq_entry_callback+0x50/0x50 ? kthread+0x153/0x170 ? __kthread_bind_mask+0x60/0x60 ? ret_from_fork+0x22/0x30 While running osnoise tracer with other tracers that rely on synchronize_rcu_tasks(), where that just hung. The reason is that osnoise_main() never schedules out if the interval is less than 1, and this will cause synchronize_rcu_tasks() to never return. Link: https://lkml.kernel.org/r/20210628114953.6dc06a91@oasis.local.home Fixes: bce29ac9ce0bb ("trace: Add osnoise tracer") Acked-by: Paul E. McKenney Reviewed-by: Daniel Bristot de Oliveira Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_osnoise.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index 38aa5e208ffd..556d530af805 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -1216,8 +1216,11 @@ static int osnoise_main(void *data) * differently from hwlat_detector, the osnoise tracer can run * without a pause because preemption is on. */ - if (interval < 1) + if (interval < 1) { + /* Let synchronize_rcu_tasks() make progress */ + cond_resched_tasks_rcu_qs(); continue; + } if (msleep_interruptible(interval)) break; -- 2.34.1