Commit-ID: ac99c58c9e56967037382e31f865b72b10127965
Gitweb: http://git.kernel.org/tip/ac99c58c9e56967037382e31f865b72b10127965
Author: Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Sun, 15 Mar 2009 22:10:35 +0100
Commit: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Mon, 16 Mar 2009 09:13:15 +0100
tracing/syscalls: fix missing release of tracing
Impact: fix 'stuck' syscall tracer
The syscall tracer uses a refcounter to enable several users
simultaneously.
But the refcounter did not behave correctly and always restored
its value to 0 after calling start_syscall_tracing(). Therefore,
stop_syscall_tracing() couldn't release correctly the tasks from
tracing.
Also the tracer forgot to reset the buffer when it is released.
Drop the pointless refcount decrement on start_syscall_tracing()
and reset the buffer when we release the tracer.
This fixes two reported issue:
- when we switch from syscall tracer to another tracer, syscall
tracing continued.
- incorrect use of the refcount.
Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reported-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
LKML-Reference: <1237151439-6755-1-git-send-email-fweisbec@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/trace/trace_syscalls.c | 11 +++++------
1 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index c72e599..c5fc1d8 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -96,8 +96,9 @@ void start_ftrace_syscalls(void)
unsigned long flags;
struct task_struct *g, *t;
+ /* Don't enable the flag on the tasks twice */
if (atomic_inc_return(&refcount) != 1)
- goto out;
+ return;
arch_init_ftrace_syscalls();
read_lock_irqsave(&tasklist_lock, flags);
@@ -107,8 +108,6 @@ void start_ftrace_syscalls(void)
} while_each_thread(g, t);
read_unlock_irqrestore(&tasklist_lock, flags);
-out:
- atomic_dec(&refcount);
}
void stop_ftrace_syscalls(void)
@@ -116,8 +115,9 @@ void stop_ftrace_syscalls(void)
unsigned long flags;
struct task_struct *g, *t;
+ /* There are perhaps still some users */
if (atomic_dec_return(&refcount))
- goto out;
+ return;
read_lock_irqsave(&tasklist_lock, flags);
@@ -126,8 +126,6 @@ void stop_ftrace_syscalls(void)
} while_each_thread(g, t);
read_unlock_irqrestore(&tasklist_lock, flags);
-out:
- atomic_inc(&refcount);
}
void ftrace_syscall_enter(struct pt_regs *regs)
@@ -201,6 +199,7 @@ static int init_syscall_tracer(struct trace_array *tr)
static void reset_syscall_tracer(struct trace_array *tr)
{
stop_ftrace_syscalls();
+ tracing_reset_online_cpus(tr);
}
static struct trace_event syscall_enter_event = {
--
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