From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Carsten Emde <C.Emde@osadl.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
John Kacur <jkacur@redhat.com>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
<stable-rt@vger.kernel.org>
Subject: [PATCH RT 14/15] trace: correct off by one while recording the trace-event
Date: Tue, 12 Jul 2016 10:29:21 -0400 [thread overview]
Message-ID: <20160712142920.931345303@goodmis.org> (raw)
In-Reply-To: 20160712142907.636678217@goodmis.org
[-- Attachment #1: 0014-trace-correct-off-by-one-while-recording-the-trace-e.patch --]
[-- Type: text/plain, Size: 1432 bytes --]
3.18.36-rt38-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Trace events like raw_syscalls show always a preempt code of one. The
reason is that on PREEMPT kernels rcu_read_lock_sched_notrace()
increases the preemption counter and the function recording the counter
is caller within the RCU section.
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[ Changed this to upstream version. See commit e947841c0dce ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_events.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index b6dd7f3bfc03..7bf7478c3e38 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -200,6 +200,14 @@ void *ftrace_event_buffer_reserve(struct ftrace_event_buffer *fbuffer,
local_save_flags(fbuffer->flags);
fbuffer->pc = preempt_count();
+ /*
+ * If CONFIG_PREEMPT is enabled, then the tracepoint itself disables
+ * preemption (adding one to the preempt_count). Since we are
+ * interested in the preempt_count at the time the tracepoint was
+ * hit, we need to subtract one to offset the increment.
+ */
+ if (IS_ENABLED(CONFIG_PREEMPT))
+ fbuffer->pc--;
fbuffer->ftrace_file = ftrace_file;
fbuffer->event =
--
2.8.1
next prev parent reply other threads:[~2016-07-12 14:29 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-12 14:29 [PATCH RT 00/15] Linux 3.18.36-rt38-rc1 Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 01/15] kvm, rt: change async pagefault code locking for PREEMPT_RT Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 02/15] mm/zsmalloc: Use get/put_cpu_light in zs_map_object()/zs_unmap_object() Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 03/15] net: dev: always take qdiscs busylock in __dev_xmit_skb() Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 04/15] drivers/block/zram: Replace bit spinlocks with rtmutex for -rt Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 05/15] list_bl: fixup bogus lockdep warning Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 06/15] ARM: imx: always use TWD on IMX6Q Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 07/15] drivers/block/zram: fixup compile for !RT Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 08/15] perf/x86/intel/rapl: Make PMU lock raw Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 09/15] sched,preempt: Fix preempt_count manipulations Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 10/15] kernel/printk: Dont try to print from IRQ/NMI region Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 11/15] arm: lazy preempt: correct resched condition Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 12/15] locallock: add local_lock_on() Steven Rostedt
2016-07-12 14:29 ` [PATCH RT 13/15] mm: perform lru_add_drain_all() remotely Steven Rostedt
2016-07-12 14:29 ` Steven Rostedt [this message]
2016-07-12 14:29 ` [PATCH RT 15/15] Linux 3.18.36-rt38-rc1 Steven Rostedt
2016-07-12 23:20 ` Linux 3.18.36-rt38-rc2 Steven Rostedt
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