hi,
Hello Xiaoguang Wang,
The patch e0c06f5ab2c5: "io_uring: refactor io_sq_thread() handling"
from Nov 3, 2020, leads to the following static checker warning:
fs/io_uring.c:6939 io_sq_thread()
error: uninitialized symbol 'timeout'.
fs/io_uring.c
6883 static int io_sq_thread(void *data)
6884 {
6885 struct cgroup_subsys_state *cur_css = NULL;
6886 struct files_struct *old_files = current->files;
6887 struct nsproxy *old_nsproxy = current->nsproxy;
6888 struct pid *old_thread_pid = current->thread_pid;
6889 const struct cred *old_cred = NULL;
6890 struct io_sq_data *sqd = data;
6891 struct io_ring_ctx *ctx;
6892 unsigned long timeout;
^^^^^^^^^^^^^^^^^^^^^^
6893 DEFINE_WAIT(wait);
6894
6895 task_lock(current);
6896 current->files = NULL;
6897 current->nsproxy = NULL;
6898 current->thread_pid = NULL;
6899 task_unlock(current);
6900
6901 while (!kthread_should_stop()) {
6902 int ret;
6903 bool cap_entries, sqt_spin, needs_sched;
6904
6905 /*
6906 * Any changes to the sqd lists are synchronized through the
6907 * kthread parking. This synchronizes the thread vs users,
6908 * the users are synchronized on the sqd->ctx_lock.
6909 */
6910 if (kthread_should_park())
6911 kthread_parkme();
6912
6913 if (unlikely(!list_empty(&sqd->ctx_new_list))) {
6914 io_sqd_init_new(sqd);
6915 timeout = jiffies + sqd->sq_thread_idle;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
timeout not set on else path.
Thanks for the report, but indeed I think it's not a bug. When io_sq_thread
is created initially, it's not waken up to run, and once it's waken up to run,
it will see that sqd->ctx_new_list is not empty, then timeout always can be
initialized.
Regards,
Xiaoguang Wang
6916 }
6917
6918 sqt_spin = false;
6919 cap_entries = !list_is_singular(&sqd->ctx_list);
6920 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
6921 if (current->cred != ctx->creds) {
6922 if (old_cred)
6923 revert_creds(old_cred);
6924 old_cred = override_creds(ctx->creds);
6925 }
6926 io_sq_thread_associate_blkcg(ctx, &cur_css);
6927 #ifdef CONFIG_AUDIT
6928 current->loginuid = ctx->loginuid;
6929 current->sessionid = ctx->sessionid;
6930 #endif
6931
6932 ret = __io_sq_thread(ctx, cap_entries);
6933 if (!sqt_spin && (ret > 0 || !list_empty(&ctx->iopoll_list)))
6934 sqt_spin = true;
6935
6936 io_sq_thread_drop_mm_files();
6937 }
6938
6939 if (sqt_spin || !time_after(jiffies, timeout)) {
^^^^^^^
warning
6940 io_run_task_work();
6941 cond_resched();
6942 if (sqt_spin)
6943 timeout = jiffies + sqd->sq_thread_idle;
6944 continue;
6945 }
6946
6947 if (kthread_should_park())
6948 continue;
6949
6950 needs_sched = true;
6951 prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
6952 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
6953 if ((ctx->flags & IORING_SETUP_IOPOLL) &&
6954 !list_empty_careful(&ctx->iopoll_list)) {
6955 needs_sched = false;
6956 break;
6957 }
6958 if (io_sqring_entries(ctx)) {
6959 needs_sched = false;
6960 break;
6961 }
6962 }
6963
6964 if (needs_sched) {
6965 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
6966 io_ring_set_wakeup_flag(ctx);
6967
6968 schedule();
6969 list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
6970 io_ring_clear_wakeup_flag(ctx);
6971 }
6972
6973 finish_wait(&sqd->wait, &wait);
6974 timeout = jiffies + sqd->sq_thread_idle;
6975 }
6976
6977 io_run_task_work();
6978
6979 if (cur_css)
6980 io_sq_thread_unassociate_blkcg();
6981 if (old_cred)
6982 revert_creds(old_cred);
6983
6984 task_lock(current);
6985 current->files = old_files;
6986 current->nsproxy = old_nsproxy;
6987 current->thread_pid = old_thread_pid;
6988 task_unlock(current);
6989
6990 kthread_parkme();
6991
6992 return 0;
6993 }
regards,
dan carpenter
