From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
Petr Mladek <pmladek@suse.com>
Subject: [PATCH 03/11 v2] ftrace: Optimize testing what context current is in
Date: Fri, 30 Oct 2020 17:31:45 -0400 [thread overview]
Message-ID: <20201030214013.510163165@goodmis.org> (raw)
In-Reply-To: 20201030213142.096102821@goodmis.org
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
The preempt_count() is not a simple location in memory, it could be part of
per_cpu code or more. Each access to preempt_count(), or one of its accessor
functions (like in_interrupt()) takes several cycles. By reading
preempt_count() once, and then doing tests to find the context against the
value return is slightly faster than using in_nmi() and in_interrupt().
Link: https://lkml.kernel.org/r/20201028115612.780796355@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
include/linux/trace_recursion.h | 33 ++++++++++++++++++++-------------
1 file changed, 20 insertions(+), 13 deletions(-)
diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index f2a949dbfec7..ac3d73484cb2 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -117,22 +117,29 @@ enum {
#define TRACE_CONTEXT_MASK TRACE_LIST_MAX
+/*
+ * Used for setting context
+ * NMI = 0
+ * IRQ = 1
+ * SOFTIRQ = 2
+ * NORMAL = 3
+ */
+enum {
+ TRACE_CTX_NMI,
+ TRACE_CTX_IRQ,
+ TRACE_CTX_SOFTIRQ,
+ TRACE_CTX_NORMAL,
+};
+
static __always_inline int trace_get_context_bit(void)
{
- int bit;
-
- if (in_interrupt()) {
- if (in_nmi())
- bit = 0;
-
- else if (in_irq())
- bit = 1;
- else
- bit = 2;
- } else
- bit = 3;
+ unsigned long pc = preempt_count();
- return bit;
+ if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
+ return TRACE_CTX_NORMAL;
+ else
+ return pc & NMI_MASK ? TRACE_CTX_NMI :
+ pc & HARDIRQ_MASK ? TRACE_CTX_IRQ : TRACE_CTX_SOFTIRQ;
}
static __always_inline int trace_test_and_set_recursion(int start, int max)
--
2.28.0
next prev parent reply other threads:[~2020-10-30 21:40 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-30 21:31 [PATCH 00/11 v2] ftrace: Have callbacks handle their own recursion Steven Rostedt
2020-10-30 21:31 ` [PATCH 01/11 v2] ftrace: Move the recursion testing into global headers Steven Rostedt
2020-10-30 21:31 ` [PATCH 02/11 v2] ftrace: Add ftrace_test_recursion_trylock() helper function Steven Rostedt
2020-10-30 21:31 ` Steven Rostedt [this message]
2020-10-30 21:31 ` [PATCH 04/11 v2] pstore/ftrace: Add recursion protection to the ftrace callback Steven Rostedt
2020-10-30 21:31 ` [PATCH 05/11 v2] kprobes/ftrace: " Steven Rostedt
2020-11-03 11:22 ` Masami Hiramatsu
2020-11-04 18:46 ` [PATCH 05/11 v2.1] " Steven Rostedt
2020-10-30 21:31 ` [PATCH 06/11 v2] livepatch/ftrace: " Steven Rostedt
2020-10-30 21:31 ` [PATCH 07/11 v2] livepatch: Trigger WARNING if livepatch function fails due to recursion Steven Rostedt
2020-11-02 14:41 ` Petr Mladek
2020-11-02 16:56 ` Steven Rostedt
2020-10-30 21:31 ` [PATCH 08/11 v2] perf/ftrace: Add recursion protection to the ftrace callback Steven Rostedt
2020-10-30 21:31 ` [PATCH 09/11 v2] perf/ftrace: Check for rcu_is_watching() in callback function Steven Rostedt
2020-10-30 21:31 ` [PATCH 10/11 v2] ftrace: Reverse what the RECURSION flag means in the ftrace_ops Steven Rostedt
2020-10-30 21:31 ` [PATCH 11/11 v2] ftrace: Add recording of functions that caused recursion Steven Rostedt
2020-11-02 16:41 ` Petr Mladek
2020-11-02 17:09 ` Steven Rostedt
2020-11-02 17:19 ` Steven Rostedt
2020-11-03 10:40 ` Petr Mladek
2020-11-02 17:37 ` Steven Rostedt
2020-11-02 17:46 ` Steven Rostedt
2020-11-02 19:23 ` [PATCH 11/11 v2.2] " Steven Rostedt
2020-11-03 14:10 ` Petr Mladek
2020-11-03 16:14 ` Steven Rostedt
2020-11-04 19:13 ` Steven Rostedt
2020-11-02 19:14 ` [PATCH 11/11 v2.1] " Steven Rostedt
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