On 10/4/21 1:21 PM, Mike Christie wrote:
> The kthread API creates threads that ignore all signals by default so
> modules like vhost that will move from that API to kernel_worker will
> not be expecting them. This patch adds a worker flag that tells
> kernel_worker to setup the task to ignore signals.
>
> Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
> Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
> ---
> include/linux/sched/task.h | 1 +
> kernel/fork.c | 11 ++++++++++-
> 2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
> index 781abbc1c288..aefa0d221b57 100644
> --- a/include/linux/sched/task.h
> +++ b/include/linux/sched/task.h
> @@ -21,6 +21,7 @@ struct css_set;
> #define KERN_WORKER_IO BIT(0)
> #define KERN_WORKER_USER BIT(1)
> #define KERN_WORKER_NO_FILES BIT(2)
> +#define KERN_WORKER_NO_SIGS BIT(3)
>
> struct kernel_clone_args {
> u64 flags;
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 3f3fcabffa5f..34d3dca70cfb 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2555,6 +2555,8 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
> struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node,
> unsigned long clone_flags, u32 worker_flags)
> {
> + struct task_struct *tsk;
> +
> struct kernel_clone_args args = {
> .flags = ((lower_32_bits(clone_flags) | CLONE_VM |
> CLONE_UNTRACED) & ~CSIGNAL),
> @@ -2564,7 +2566,14 @@ struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node,
> .worker_flags = KERN_WORKER_USER | worker_flags,
> };
>
> - return copy_process(NULL, 0, node, &args);
> + tsk = copy_process(NULL, 0, node, &args);
> + if (IS_ERR(tsk))
> + return tsk;
> +
> + if (worker_flags & KERN_WORKER_NO_SIGS)
> + ignore_signals(tsk);
> +
> + return tsk;
When I originally did it this way, Eric (correctly) pointed out that
it's racy. See where it's currently done as part of copy_process(), not
after.
--
Jens Axboe
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