[PATCH 1/5] tracing: convert ftrace_dump spinlocks to raw

Steven Rostedt
2009-04-29T04:59:51Z

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From: Steven Rostedt <srostedt@redhat.com>

ftrace_dump is used for printing out the contents of the ftrace ring buffer
to the console on failure. Currently it uses a spinlock to synchronize
the output from multiple failures on different CPUs. This spin lock
currently is a normal spinlock and can cause issues with lockdep and
lock tracing.

This patch converts it to raw since it is for error handling only.
The lock is local to the ftrace_dump and is not used by any other
infrastructure.

[ Impact: prevent ftrace_dump from locking up by internal tracing ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b6183bc..5d704a4 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4114,7 +4114,8 @@ trace_printk_seq(struct trace_seq *s)

static void __ftrace_dump(bool disable_tracing)
{
- static DEFINE_SPINLOCK(ftrace_dump_lock);
+ static raw_spinlock_t ftrace_dump_lock =
+ (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
/* use static because iter can be a bit big for the stack */
static struct trace_iterator iter;
unsigned int old_userobj;
@@ -4123,7 +4124,8 @@ static void __ftrace_dump(bool disable_tracing)
int cnt = 0, cpu;

/* only one dump */
- spin_lock_irqsave(&ftrace_dump_lock, flags);
+ local_irq_save(flags);
+ __raw_spin_lock(&ftrace_dump_lock);
if (dump_ran)
goto out;

@@ -4195,7 +4197,8 @@ static void __ftrace_dump(bool disable_tracing)
}

out:
- spin_unlock_irqrestore(&ftrace_dump_lock, flags);
+ __raw_spin_unlock(&ftrace_dump_lock);
+ local_irq_restore(flags);
}

/* By default: disable tracing after the dump */
--
1.6.2.1

--