Messages in this thread | | | Date | Thu, 05 Mar 2015 13:18:25 +0200 | From | Alex Dowad <> | Subject | Re: [PATCH] do_fork(): Rename 'stack_size' argument to reflect actual use |
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On 05/03/15 01:07, David Rientjes wrote: > On Wed, 4 Mar 2015, Alex Dowad wrote: > >> The 'stack_size' argument is never used to pass a stack size. It's only used when >> forking a kernel thread, in which case it is an argument which should be passed >> to the 'main' function which the kernel thread executes. Hence, rename it to >> 'kthread_arg'. >> >> Signed-off-by: Alex Dowad <alexinbeijing@gmail.com> >> --- >> >> Hi, >> >> Please have a look at this patch. If this is accepted, I have a series of patches >> ready for a similar cleanup to all the arch-specific implementations of copy_thread() >> (as suggested by Andrew Morton in a private e-mail). >> >> Thank you, >> Alex Dowad >> >> kernel/fork.c | 14 ++++++++------ >> 1 file changed, 8 insertions(+), 6 deletions(-) >> >> diff --git a/kernel/fork.c b/kernel/fork.c >> index cf65139..b38a2ae 100644 >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -1186,10 +1186,12 @@ init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) >> * It copies the registers, and all the appropriate >> * parts of the process environment (as per the clone >> * flags). The actual kick-off is left to the caller. >> + * >> + * When copying a kernel thread, 'stack_start' is the function to run. >> */ >> static struct task_struct *copy_process(unsigned long clone_flags, >> unsigned long stack_start, >> - unsigned long stack_size, >> + unsigned long kthread_arg, >> int __user *child_tidptr, >> struct pid *pid, >> int trace) >> @@ -1401,7 +1403,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, >> retval = copy_io(clone_flags, p); >> if (retval) >> goto bad_fork_cleanup_namespaces; >> - retval = copy_thread(clone_flags, stack_start, stack_size, p); >> + retval = copy_thread(clone_flags, stack_start, kthread_arg, p); >> if (retval) >> goto bad_fork_cleanup_io; >> >> @@ -1629,8 +1631,8 @@ struct task_struct *fork_idle(int cpu) >> * it and waits for it to finish using the VM if required. >> */ >> long do_fork(unsigned long clone_flags, >> - unsigned long stack_start, >> - unsigned long stack_size, >> + unsigned long stack_start, /* or function for kthread to run */ >> + unsigned long kthread_arg, >> int __user *parent_tidptr, >> int __user *child_tidptr) >> { > Looks fine, but I'm not sure about commenting functional formals. Since > copy_process() and do_fork() can have formals with different meanings, > then why not just rename them "arg1" and "arg2" respectively and then > define in the comment above the function what the possible combinations > are?
The second argument is *only* ever used for one thing: an argument passed to a kernel thread. That's why I would like to rename it to "kthread_arg". The previous argument (currently named "stack_start") is indeed used for 2 different things: a new stack pointer for a user thread, or a function to be executed by a kernel thread. Rather than "arg1", what would you think of something like "sp_or_fn", or "usp_or_fn"?
Thanks for your feedback!
> >> @@ -1656,7 +1658,7 @@ long do_fork(unsigned long clone_flags, >> trace = 0; >> } >> >> - p = copy_process(clone_flags, stack_start, stack_size, >> + p = copy_process(clone_flags, stack_start, kthread_arg, >> child_tidptr, NULL, trace); >> /* >> * Do this prior waking up the new thread - the thread pointer >> @@ -1740,7 +1742,7 @@ SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags, >> int, tls_val) >> #elif defined(CONFIG_CLONE_BACKWARDS3) >> SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp, >> - int, stack_size, >> + int, ignored, >> int __user *, parent_tidptr, >> int __user *, child_tidptr, >> int, tls_val)
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