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Subject[RFC PATCH 1/6] thread_info: Add update_thread_flag() helpers
Date
There are a number of bits of code sprinkled around the kernel to
set a thread flag if a certain condition is true, and clear it
otherwise.

To help make those call sites terser and less cumbersome, this
patch adds a new family of thread flag manipulators

update*_thread_flag([...,] flag, cond)

which do the equivalent of:

if (cond)
set*_thread_flag([...,] flag);
else
clear*_thread_flag([...,] flag);

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
---

Note, this patch assumes C99 _Bool semantics where casting a value to
_Bool is true is and only if the value compares != 0. This would not
be true if bool where a typedef of unsigned char for example.

It appears that the kernel has always used the C99 semantics for bool
and relies on them elsewhere, so I don't believe this patch introduces
a new dependency.
---
include/linux/sched.h | 6 ++++++
include/linux/thread_info.h | 11 +++++++++++
include/trace/syscall.h | 6 ++----
kernel/ptrace.c | 13 +++++--------
4 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index b3d697f..c2c3051 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1578,6 +1578,12 @@ static inline void clear_tsk_thread_flag(struct task_struct *tsk, int flag)
clear_ti_thread_flag(task_thread_info(tsk), flag);
}

+static inline void update_tsk_thread_flag(struct task_struct *tsk, int flag,
+ bool value)
+{
+ update_ti_thread_flag(task_thread_info(tsk), flag, value);
+}
+
static inline int test_and_set_tsk_thread_flag(struct task_struct *tsk, int flag)
{
return test_and_set_ti_thread_flag(task_thread_info(tsk), flag);
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 34f053a..efd5ec4 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -64,6 +64,15 @@ static inline void clear_ti_thread_flag(struct thread_info *ti, int flag)
clear_bit(flag, (unsigned long *)&ti->flags);
}

+static inline void update_ti_thread_flag(struct thread_info *ti, int flag,
+ bool value)
+{
+ if (value)
+ set_ti_thread_flag(ti, flag);
+ else
+ clear_ti_thread_flag(ti, flag);
+}
+
static inline int test_and_set_ti_thread_flag(struct thread_info *ti, int flag)
{
return test_and_set_bit(flag, (unsigned long *)&ti->flags);
@@ -83,6 +92,8 @@ static inline int test_ti_thread_flag(struct thread_info *ti, int flag)
set_ti_thread_flag(current_thread_info(), flag)
#define clear_thread_flag(flag) \
clear_ti_thread_flag(current_thread_info(), flag)
+#define update_thread_flag(flag, value) \
+ update_ti_thread_flag(current_thread_info(), flag, value)
#define test_and_set_thread_flag(flag) \
test_and_set_ti_thread_flag(current_thread_info(), flag)
#define test_and_clear_thread_flag(flag) \
diff --git a/include/trace/syscall.h b/include/trace/syscall.h
index dc8ac27..dcc9bdf 100644
--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h
@@ -37,10 +37,8 @@ struct syscall_metadata {
#if defined(CONFIG_TRACEPOINTS) && defined(CONFIG_HAVE_SYSCALL_TRACEPOINTS)
static inline void syscall_tracepoint_update(struct task_struct *p)
{
- if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
- set_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT);
- else
- clear_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT);
+ update_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT,
+ test_thread_flag(TIF_SYSCALL_TRACEPOINT));
}
#else
static inline void syscall_tracepoint_update(struct task_struct *p)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 21fec73..7a2bd8d 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -785,16 +785,13 @@ static int ptrace_resume(struct task_struct *child, long request,
if (!valid_signal(data))
return -EIO;

- if (request == PTRACE_SYSCALL)
- set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
- else
- clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+ update_tsk_thread_flag(child, TIF_SYSCALL_TRACE,
+ request == PTRACE_SYSCALL);

#ifdef TIF_SYSCALL_EMU
- if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
- set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
- else
- clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
+ update_tsk_thread_flag(child, TIF_SYSCALL_EMU,
+ request == PTRACE_SYSEMU ||
+ request == PTRACE_SYSEMU_SINGLESTEP);
#endif

if (is_singleblock(request)) {
--
2.1.4
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