From: "Eric W. Biederman" <ebiederm@xmission.com>
To: linux-arch@vger.kernel.org
Cc: Tejun Heo <tj@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Al Viro <viro@ZenIV.linux.org.uk>, Jens Axboe <axboe@kernel.dk>,
Thomas Gleixner <tglx@linutronix.de>,
Linus Torvalds <torvalds@linuxfoundation.org>,
linux-kernel@vger.kernel.org,
"Eric W. Biederman" <ebiederm@xmission.com>
Subject: [PATCH 3/7] fork: Explicity test for idle tasks in copy_thread
Date: Fri, 6 May 2022 09:15:08 -0500 [thread overview]
Message-ID: <20220506141512.516114-3-ebiederm@xmission.com> (raw)
In-Reply-To: <87mtfu4up3.fsf@email.froward.int.ebiederm.org>
The architectures ia64 and parisc have special handling for the idle
thread in copy_process. Add a flag named idle to kernel_clone_args
and use it to explicity test if an idle process is being created.
Fullfill the expectations of the rest of the copy_thread
implemetations and pass a function pointer in .stack from fork_idle().
This makes what is happening in copy_thread better defined, and is
useful to make idle threads less special.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
arch/ia64/kernel/process.c | 2 +-
arch/parisc/kernel/process.c | 2 +-
include/linux/sched/task.h | 1 +
kernel/fork.c | 9 +++++++++
4 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index 10d41ded05a5..8f010ae818bc 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -342,7 +342,7 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
ia64_drop_fpu(p); /* don't pick up stale state from a CPU's fph */
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
- if (unlikely(!user_stack_base)) {
+ if (unlikely(args->idle)) {
/* fork_idle() called us */
return 0;
}
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 129c17de45ba..30a5874ca845 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -224,7 +224,7 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
/* kernel thread */
memset(cregs, 0, sizeof(struct pt_regs));
- if (!usp) /* idle thread */
+ if (args->idle) /* idle thread */
return 0;
/* Must exit via ret_from_kernel_thread in order
* to call schedule_tail()
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index fcdcba231aac..3d6b99ce5408 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -33,6 +33,7 @@ struct kernel_clone_args {
int cgroup;
int io_thread;
int kthread;
+ int idle;
struct cgroup *cgrp;
struct css_set *cset;
};
diff --git a/kernel/fork.c b/kernel/fork.c
index d39a248a8d8d..93d77ee921ff 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2544,12 +2544,21 @@ static inline void init_idle_pids(struct task_struct *idle)
}
}
+static int idle_dummy(void *dummy)
+{
+ /* This function is never called */
+ return 0;
+}
+
struct task_struct * __init fork_idle(int cpu)
{
struct task_struct *task;
struct kernel_clone_args args = {
.flags = CLONE_VM,
+ .stack = (unsigned long)&idle_dummy,
+ .stack_size = (unsigned long)NULL,
.kthread = 1,
+ .idle = 1,
};
task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args);
--
2.35.3
next prev parent reply other threads:[~2022-05-06 14:15 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CANpfEhOnNZa5d_G3e0dzzbbEtSuqxWY-fUCqzSiFpiQ2k0hJyw@mail.gmail.com>
[not found] ` <CAHk-=wjfecvcUk2vNQM1GiUz_G=WQEJ8i8JS7yjnxjq_f-OgKw@mail.gmail.com>
[not found] ` <87a6czifo7.fsf@email.froward.int.ebiederm.org>
[not found] ` <CAHk-=wj=EHvH-DEUHbkoB3vDZJ1xRzrk44JibtNOepNkachxPw@mail.gmail.com>
[not found] ` <87ilrn1drx.ffs@tglx>
[not found] ` <877d7zk1cf.ffs@tglx>
[not found] ` <CAHk-=wiJPeANKYU4imYaeEuV6sNP+EDR=rWURSKv=y4Mhcn1hA@mail.gmail.com>
[not found] ` <87y20fid4d.ffs@tglx>
[not found] ` <87bkx5q3pk.fsf_-_@email.froward.int.ebiederm.org>
2022-05-06 14:11 ` [PATCH 0/7] fork: Make init and umh ordinary tasks Eric W. Biederman
2022-05-06 14:15 ` [PATCH 1/7] kthread: Don't allocate kthread_struct for init and umh Eric W. Biederman
[not found] ` <CANpfEhNAQvazzCSN-dVgYmwNSRjqOrqZF0_j7GPLbCdEkogzSg@mail.gmail.com>
2022-05-06 20:53 ` Eric W. Biederman
2022-05-10 14:38 ` Thomas Gleixner
2022-05-10 15:14 ` Eric W. Biederman
2022-05-11 17:41 ` Eric W. Biederman
2022-05-06 14:15 ` [PATCH 2/7] fork: Pass struct kernel_clone_args into copy_thread Eric W. Biederman
2022-05-06 20:38 ` kernel test robot
2022-05-06 21:52 ` Eric W. Biederman
2022-05-06 14:15 ` Eric W. Biederman [this message]
2022-05-06 14:15 ` [PATCH 4/7] fork: Generalize PF_IO_WORKER handling Eric W. Biederman
2022-05-06 14:15 ` [PATCH 5/7] init: Deal with the init process being a user mode process Eric W. Biederman
2022-05-06 14:15 ` [PATCH 6/7] fork: Explicitly set PF_KTHREAD Eric W. Biederman
2022-05-06 14:15 ` [PATCH 7/7] fork: Stop allowing kthreads to call execve Eric W. Biederman
2022-05-09 20:46 ` [PATCH 0/7] fork: Make init and umh ordinary tasks Qian Cai
2022-05-09 21:52 ` Eric W. Biederman
2022-05-10 15:36 ` Qian Cai
2022-05-11 17:37 ` [PATCH 8/7] sched: Update task_tick_numa to ignore tasks without an mm Eric W. Biederman
2022-05-11 17:42 ` Linus Torvalds
2022-05-11 17:53 ` Eric W. Biederman
2022-05-11 17:59 ` Linus Torvalds
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