Mailing List Archive

I saw some RCU illegal usage from idle complaints when function tracer
is enabled with forced context tracking.

It seems that __schedule() might be called in function_trace_call() when
it re-enables preemption(if preemption and irqs are both enabled).

So at the places where we call rcu_user_exit(), we need make sure that
no function tracer hooks could be called in preemption/irqs both enabled
environment before rcu_user_exit() finishes, or we might cause illegal
RCU usage in __schedule().

This patch tries to add notrace attribute to a couple of functions where
the above could happen, including user_exit(), and a few callers of
user_exit().

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
--
arch/x86/kernel/ptrace.c | 4 ++--
arch/x86/kernel/signal.c | 2 +-
include/linux/rcupdate.h | 2 ++
kernel/context_tracking.c | 2 +-
kernel/sched/core.c | 2 +-
5 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 29a8120..04659c2 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1488,7 +1488,7 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
* We must return the syscall number to actually look up in the table.
* This can be -1L to skip running any syscall at all.
*/
-long syscall_trace_enter(struct pt_regs *regs)
+long rcu_user_notrace syscall_trace_enter(struct pt_regs *regs)
{
long ret = 0;

@@ -1538,7 +1538,7 @@ out:
return ret ?: regs->orig_ax;
}

-void syscall_trace_leave(struct pt_regs *regs)
+void rcu_user_notrace syscall_trace_leave(struct pt_regs *regs)
{
bool step;

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 6956299..10a9e5a 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -732,7 +732,7 @@ static void do_signal(struct pt_regs *regs)
* notification of userspace execution resumption
* - triggered by the TIF_WORK_MASK flags
*/
-void
+void rcu_user_notrace
do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
{
user_exit();
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index b758ce1..ecf9872 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -229,6 +229,7 @@ extern void rcu_user_enter(void);
extern void rcu_user_exit(void);
extern void rcu_user_enter_after_irq(void);
extern void rcu_user_exit_after_irq(void);
+#define rcu_user_notrace notrace
#else
static inline void rcu_user_enter(void) { }
static inline void rcu_user_exit(void) { }
@@ -236,6 +237,7 @@ static inline void rcu_user_enter_after_irq(void) { }
static inline void rcu_user_exit_after_irq(void) { }
static inline void rcu_user_hooks_switch(struct task_struct *prev,
struct task_struct *next) { }
+#define rcu_user_notrace
#endif /* CONFIG_RCU_USER_QS */

extern void exit_rcu(void);
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 65349f0..d3fc35f 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -83,7 +83,7 @@ void user_enter(void)
* This call supports re-entrancy. This way it can be called from any exception
* handler without needing to know if we came from userspace or not.
*/
-void user_exit(void)
+void rcu_user_notrace user_exit(void)
{
unsigned long flags;

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2b52431..c970e92 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2973,7 +2973,7 @@ asmlinkage void __sched schedule(void)
EXPORT_SYMBOL(schedule);

#ifdef CONFIG_CONTEXT_TRACKING
-asmlinkage void __sched schedule_user(void)
+asmlinkage void __sched rcu_user_notrace schedule_user(void)
{
/*
* If we come here after a random call to set_need_resched(),


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/