task_work: Introduce task_work_pending

Wrap the test of task->task_works in a helper function to make
it clear what is being tested.

All of the other readers of task->task_work use READ_ONCE and this is
even necessary on current as other processes can update
task->task_work.  So for consistency I have added READ_ONCE into
task_work_pending.

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-7-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index e54c412..e852610 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2590,7 +2590,7 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
 
 static inline bool io_run_task_work(void)
 {
-       if (test_thread_flag(TIF_NOTIFY_SIGNAL) || current->task_works) {
+       if (test_thread_flag(TIF_NOTIFY_SIGNAL) || task_work_pending(current)) {
                __set_current_state(TASK_RUNNING);
                tracehook_notify_signal();
                return true;
@@ -7602,7 +7602,7 @@ static int io_sq_thread(void *data)
                }
 
                prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
-               if (!io_sqd_events_pending(sqd) && !current->task_works) {
+               if (!io_sqd_events_pending(sqd) && !task_work_pending(current)) {
                        bool needs_sched = true;
 
                        list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
@@ -10321,7 +10321,7 @@ static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx,
 
                hlist_for_each_entry(req, list, hash_node)
                        seq_printf(m, "  op=%d, task_works=%d\n", req->opcode,
-                                       req->task->task_works != NULL);
+                                       task_work_pending(req->task));
        }
 
        seq_puts(m, "CqOverflowList:\n");

diff --git a/include/linux/task_work.h b/include/linux/task_work.h
index 5b8a93f..897494b 100644 (file)
--- a/include/linux/task_work.h
+++ b/include/linux/task_work.h
@@ -19,6 +19,11 @@ enum task_work_notify_mode {
        TWA_SIGNAL,
 };
 
+static inline bool task_work_pending(struct task_struct *task)
+{
+       return READ_ONCE(task->task_works);
+}
+
 int task_work_add(struct task_struct *task, struct callback_head *twork,
                        enum task_work_notify_mode mode);
 

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index b77bf49..fa834a2 100644 (file)
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -90,7 +90,7 @@ static inline void tracehook_notify_resume(struct pt_regs *regs)
         * hlist_add_head(task->task_works);
         */
        smp_mb__after_atomic();
-       if (unlikely(current->task_works))
+       if (unlikely(task_work_pending(current)))
                task_work_run();
 
 #ifdef CONFIG_KEYS_REQUEST_CACHE
@@ -115,7 +115,7 @@ static inline void tracehook_notify_signal(void)
 {
        clear_thread_flag(TIF_NOTIFY_SIGNAL);
        smp_mb__after_atomic();
-       if (current->task_works)
+       if (task_work_pending(current))
                task_work_run();
 }
 

diff --git a/kernel/signal.c b/kernel/signal.c
index 0e0bd1c..3b4cf25 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2344,7 +2344,7 @@ static void ptrace_do_notify(int signr, int exit_code, int why)
 void ptrace_notify(int exit_code)
 {
        BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
-       if (unlikely(current->task_works))
+       if (unlikely(task_work_pending(current)))
                task_work_run();
 
        spin_lock_irq(&current->sighand->siglock);
@@ -2626,7 +2626,7 @@ bool get_signal(struct ksignal *ksig)
        struct signal_struct *signal = current->signal;
        int signr;
 
-       if (unlikely(current->task_works))
+       if (unlikely(task_work_pending(current)))
                task_work_run();
 
        /*

diff --git a/kernel/task_work.c b/kernel/task_work.c
index 1698fbe..cc6fccb 100644 (file)
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -78,7 +78,7 @@ task_work_cancel_match(struct task_struct *task,
        struct callback_head *work;
        unsigned long flags;
 
-       if (likely(!task->task_works))
+       if (likely(!task_work_pending(task)))
                return NULL;
        /*
         * If cmpxchg() fails we continue without updating pprev.