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| author | Christian Brauner <brauner@kernel.org> | 2026-08-24 14:08:16 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2026-08-31 10:05:12 +0200 |
| commit | 22b7f491be8f93ff72de0a3fe02b8ee9e64d3f21 (patch) | |
| tree | 1ad3a99f2d73ec389985f2a1e4e0df043bda9776 /include/linux | |
| parent | cee9395acd8043be0644b25c34bfa86623f2b935 (diff) | |
| download | linux-next-22b7f491be8f93ff72de0a3fe02b8ee9e64d3f21.tar.gz linux-next-22b7f491be8f93ff72de0a3fe02b8ee9e64d3f21.zip | |
signal: allow taks to temporarily block TIF_NOTIFY_SIGNAL
TIF_NOTIFY_SIGNAL is used to kick a task in uninterruptible sleep to
return to userspace and run task work and then go back to sleep. This
mechanism works well but breaks e.g., coredumps. dump_interrupted() only
allows fatal signals to interrupt a coredump and the whole regular write
path going to actual filesystems is impervious to TIF_NOTIFY_SIGNAL as
well.
Add PF_NO_NOTIFY_SIGNAL and helpers to raise and restore it. This is the
same approach as memalloc_nofs_save(). signal_pending() will not report
a fake pending signal via TIF_NOTIFY_SIGNAL if inside a
PF_NO_NOTIFY_SIGNAL section.
No functional changes.
Link: https://patch.msgid.link/20260824-work-tif_notify_signal-v2-1-6609e42b3157@kernel.org
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/sched.h | 2 | ||||
| -rw-r--r-- | include/linux/sched/signal.h | 27 |
2 files changed, 26 insertions, 3 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 8b3d47a325cc..e431c4195bf0 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1816,7 +1816,7 @@ extern struct pid *cad_pid; * I am cleaning dirty pages from some other bdi. */ #define PF_KTHREAD 0x00200000 /* I am a kernel thread */ #define PF_RANDOMIZE 0x00400000 /* Randomize virtual address space */ -#define PF__HOLE__00800000 0x00800000 +#define PF_NO_NOTIFY_SIGNAL 0x00800000 /* see no_notify_signal_save() */ #define PF__HOLE__01000000 0x01000000 #define PF__HOLE__02000000 0x02000000 #define PF_NO_SETAFFINITY 0x04000000 /* Userland is not allowed to meddle with cpus_mask */ diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 584ae88b435e..6164995da980 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -2,6 +2,7 @@ #ifndef _LINUX_SCHED_SIGNAL_H #define _LINUX_SCHED_SIGNAL_H +#include <linux/cleanup.h> #include <linux/rculist.h> #include <linux/signal.h> #include <linux/sched.h> @@ -384,14 +385,36 @@ static inline int task_sigpending(struct task_struct *p) return unlikely(test_tsk_thread_flag(p,TIF_SIGPENDING)); } +/* Prevent TIF_NOTIFY_SIGNAL from interrupting this task. */ +static inline unsigned int no_notify_signal_save(void) +{ + unsigned int flags = current->flags; + + current->flags |= PF_NO_NOTIFY_SIGNAL; + return flags; +} + +/* Restore the previous PF_NO_NOTIFY_SIGNAL state. */ +static inline void no_notify_signal_restore(unsigned int flags) +{ + current_restore_flags(flags, PF_NO_NOTIFY_SIGNAL); +} + +DEFINE_LOCK_GUARD_0(no_notify_signal, + _T->flags = no_notify_signal_save(), + no_notify_signal_restore(_T->flags), + unsigned int flags) + static inline int signal_pending(struct task_struct *p) { /* * TIF_NOTIFY_SIGNAL isn't really a signal, but it requires the same * behavior in terms of ensuring that we break out of wait loops - * so that notify signal callbacks can be processed. + * so that notify signal callbacks can be processed. Not for a task + * that asked not to be interrupted by it, see no_notify_signal_save(). */ - if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL))) + if (unlikely(test_tsk_thread_flag(p, TIF_NOTIFY_SIGNAL)) && + likely(!(READ_ONCE(p->flags) & PF_NO_NOTIFY_SIGNAL))) return 1; return task_sigpending(p); } |