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Date: Mon, 30 Apr 2018 18:41:59 -0700 From: Joel Fernandes <joelaf@...gle.com> To: linux-kernel@...r.kernel.org Cc: Joel Fernandes <joelaf@...gle.com>, Steven Rostedt <rostedt@...dmis.org>, Peter Zilstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Tom Zanussi <tom.zanussi@...ux.intel.com>, Namhyung Kim <namhyung@...nel.org>, Thomas Glexiner <tglx@...utronix.de>, Boqun Feng <boqun.feng@...il.com>, Paul McKenney <paulmck@...ux.vnet.ibm.com>, Frederic Weisbecker <fweisbec@...il.com>, Randy Dunlap <rdunlap@...radead.org>, Masami Hiramatsu <mhiramat@...nel.org>, Fenguang Wu <fengguang.wu@...el.com>, Baohong Liu <baohong.liu@...el.com>, Vedang Patel <vedang.patel@...el.com>, kernel-team@...roid.com Subject: [PATCH RFC v5 1/6] softirq: reorder trace_softirqs_on to prevent lockdep splat I'm able to reproduce a lockdep splat when CONFIG_PROVE_LOCKING=y and CONFIG_PREEMPTIRQ_EVENTS=y. $ echo 1 > /d/tracing/events/preemptirq/preempt_enable/enable Cc: Steven Rostedt <rostedt@...dmis.org> Cc: Peter Zilstra <peterz@...radead.org> Cc: Ingo Molnar <mingo@...hat.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com> Cc: Tom Zanussi <tom.zanussi@...ux.intel.com> Cc: Namhyung Kim <namhyung@...nel.org> Cc: Thomas Glexiner <tglx@...utronix.de> Cc: Boqun Feng <boqun.feng@...il.com> Cc: Paul McKenney <paulmck@...ux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@...il.com> Cc: Randy Dunlap <rdunlap@...radead.org> Cc: Masami Hiramatsu <mhiramat@...nel.org> Cc: Fenguang Wu <fengguang.wu@...el.com> Cc: Baohong Liu <baohong.liu@...el.com> Cc: Vedang Patel <vedang.patel@...el.com> Cc: kernel-team@...roid.com Signed-off-by: Joel Fernandes <joelaf@...gle.com> --- kernel/softirq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/kernel/softirq.c b/kernel/softirq.c index 24d243ef8e71..47e2f61938c0 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -139,9 +139,13 @@ static void __local_bh_enable(unsigned int cnt) { lockdep_assert_irqs_disabled(); + if (preempt_count() == cnt) + trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); + if (softirq_count() == (cnt & SOFTIRQ_MASK)) trace_softirqs_on(_RET_IP_); - preempt_count_sub(cnt); + + __preempt_count_sub(cnt); } /* -- 2.17.0.441.gb46fe60e1d-goog
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