tracing/kprobes: Cleanup with guard and __free | Patchew

[PATCH v2 2/6] Provide __free(argv) for argv_split() users

Masami Hiramatsu (Google) posted 6 patches 1 year, 1 month ago

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[PATCH v2 2/6] Provide __free(argv) for argv_split() users

Posted by Masami Hiramatsu (Google) 1 year, 1 month ago

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Provide __free(argv) macro for argv_split() users so that they can
avoid gotos.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 Changes in v2:
  - Fix to call argv_free() only if the argument is !IS_ERR_OR_NULL().
  - Add including cleanup.h.
---
 include/linux/string.h |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 493ac4862c77..07f2a90d5d9c 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -4,6 +4,7 @@
 
 #include <linux/args.h>
 #include <linux/array_size.h>
+#include <linux/cleanup.h>	/* for DEFINE_FREE() */
 #include <linux/compiler.h>	/* for inline */
 #include <linux/types.h>	/* for size_t */
 #include <linux/stddef.h>	/* for NULL */
@@ -312,6 +313,8 @@ extern void *kmemdup_array(const void *src, size_t count, size_t element_size, g
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
 extern void argv_free(char **argv);
 
+DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
+
 /* lib/cmdline.c */
 extern int get_option(char **str, int *pint);
 extern char *get_options(const char *str, int nints, int *ints);

DEFINE_FREE/CLASS && code readability (Was: [PATCH v2 2/6] Provide __free(argv) for argv_split() users)

Posted by Oleg Nesterov 1 year, 1 month ago

Masami,

Sorry for abusing this thread. Your patches look fine to me, it is not
that I suggest to change them. I will use your patch as an example for
off-topic discussion.

On 01/05, Masami Hiramatsu (Google) wrote:
>
> +DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))

(IS_ERR looks unneeded but this is cosmetic).

OK, so it can be used as

	void func(void)
	{
		char **argv __free(argv) = argv_split(...);
		do_something(argv);
		return;
	}

And I cry every time when I read the code like this ;)

Because, to understand this code, I need to do the "nontrivial" grep to find
"DEFINE_FREE(argv,".

Perhaps we can establish a simple rule that every DEFINE_FREE() or DEFINE_CLASS()
should add another #define? I mean something like

	DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
	#define __FREE_ARGV	__free(argv)

	void func(void)
	{
		char **argv __FREE_ARGV = argv_split(...);
		do_something(argv);
		return;
	}

This way I can press Ctrl-] and see what the cleanup code actually does.
Can save a second or two. Important when you try to read the code you are
not familiar with.

Same for DEFINE_CLASS. For example,

	int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
	{
		CLASS(fd, f)(fd);

		if (fd_empty(f))
			return -EBADF;

		return vfs_fchown(fd_file(f), user, group);
	}

If you are not familiar with this code, it looks mysterious until you find
DEFINE_CLASS(fd, ...) in include/linux/file.h.

Oleg.

Re: DEFINE_FREE/CLASS && code readability (Was: [PATCH v2 2/6] Provide __free(argv) for argv_split() users)

Posted by Masami Hiramatsu (Google) 1 year, 1 month ago

On Sun, 5 Jan 2025 15:14:22 +0100
Oleg Nesterov <oleg@redhat.com> wrote:

> Masami,
> 
> Sorry for abusing this thread. Your patches look fine to me, it is not
> that I suggest to change them. I will use your patch as an example for
> off-topic discussion.
> 
> On 01/05, Masami Hiramatsu (Google) wrote:
> >
> > +DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
> 
> (IS_ERR looks unneeded but this is cosmetic).
> 
> OK, so it can be used as
> 
> 	void func(void)
> 	{
> 		char **argv __free(argv) = argv_split(...);
> 		do_something(argv);
> 		return;
> 	}
> 
> And I cry every time when I read the code like this ;)
> 
> Because, to understand this code, I need to do the "nontrivial" grep to find
> "DEFINE_FREE(argv,".
> 
> Perhaps we can establish a simple rule that every DEFINE_FREE() or DEFINE_CLASS()
> should add another #define? I mean something like
> 
> 
> 	DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
> 	#define __FREE_ARGV	__free(argv)
> 	
> 	void func(void)
> 	{
> 		char **argv __FREE_ARGV = argv_split(...);
> 		do_something(argv);
> 		return;
> 	}
> 
> This way I can press Ctrl-] and see what the cleanup code actually does.
> Can save a second or two. Important when you try to read the code you are
> not familiar with.

That sounds lile a problem of your tool. Do you really need to find the
DEFINE_FREE() or do you think "__free(argv)" is too generic name?
If it is latter, we can make it "__free(argv_free) so that it is more
obvious to call argv_free()?

> 
> Same for DEFINE_CLASS. For example,
> 
> 	int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
> 	{
> 		CLASS(fd, f)(fd);
> 
> 		if (fd_empty(f))
> 			return -EBADF;
> 
> 		return vfs_fchown(fd_file(f), user, group);
> 	}
> 
> If you are not familiar with this code, it looks mysterious until you find
> DEFINE_CLASS(fd, ...) in include/linux/file.h.

DEFINE_CLASS() is somewhat mysterious to me too :) But if I understand
correctly, it is for intermediate macro for implementing guard().

Whether we like it or not, cleanup.h has been introduced, and it will be
more popular. What we need is a document about cleanup.h which includes
better naming conventions for its label.

BTW, I agree that 'argv' was too simple. Basically the label name of
DEFINE_FREE() is better to be a function name for free.
Let me fix that.

Thank you,

-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>

Re: DEFINE_FREE/CLASS && code readability (Was: [PATCH v2 2/6] Provide __free(argv) for argv_split() users)

Posted by Oleg Nesterov 1 year, 1 month ago

On 01/06, Masami Hiramatsu wrote:
>
> On Sun, 5 Jan 2025 15:14:22 +0100
> Oleg Nesterov <oleg@redhat.com> wrote:
>
> > Perhaps we can establish a simple rule that every DEFINE_FREE() or DEFINE_CLASS()
> > should add another #define? I mean something like
> >
> >
> > 	DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
> > 	#define __FREE_ARGV	__free(argv)
> >
> > 	void func(void)
> > 	{
> > 		char **argv __FREE_ARGV = argv_split(...);
> > 		do_something(argv);
> > 		return;
> > 	}
> >
> > This way I can press Ctrl-] and see what the cleanup code actually does.
> > Can save a second or two. Important when you try to read the code you are
> > not familiar with.
>
> That sounds lile a problem of your tool. Do you really need to find the
> DEFINE_FREE()

Yes, ":tag __free_argv" wont work. it is defined by DEFINE_FREE(argv) above.
I need to find this DEFINE_FREE(argv) to see what __free_argv() actually does.

> > Same for DEFINE_CLASS. For example,
> >
> > 	int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
> > 	{
> > 		CLASS(fd, f)(fd);
> >
> > 		if (fd_empty(f))
> > 			return -EBADF;
> >
> > 		return vfs_fchown(fd_file(f), user, group);
> > 	}
> >
> > If you are not familiar with this code, it looks mysterious until you find
> > DEFINE_CLASS(fd, ...) in include/linux/file.h.
>
> DEFINE_CLASS() is somewhat mysterious to me too :) But if I understand
> correctly, it is for intermediate macro for implementing guard().

Well, in this case you just need to find

	DEFINE_CLASS(fd, struct fd, fdput(_T), fdget(fd), int fd)

in include/linux/file.h, after that the code is clear.

> BTW, I agree that 'argv' was too simple. Basically the label name of
> DEFINE_FREE() is better to be a function name for free.
> Let me fix that.

Up to you, but __free(argv) looks good to me.

Oleg.

Re: DEFINE_FREE/CLASS && code readability (Was: [PATCH v2 2/6] Provide __free(argv) for argv_split() users)

Posted by Peter Zijlstra 1 year, 1 month ago

On Sun, Jan 05, 2025 at 03:14:22PM +0100, Oleg Nesterov wrote:

> OK, so it can be used as
> 
> 	void func(void)
> 	{
> 		char **argv __free(argv) = argv_split(...);
> 		do_something(argv);
> 		return;
> 	}
> 
> And I cry every time when I read the code like this ;)
> 
> Because, to understand this code, I need to do the "nontrivial" grep to find
> "DEFINE_FREE(argv,".
> 
> Perhaps we can establish a simple rule that every DEFINE_FREE() or DEFINE_CLASS()
> should add another #define? I mean something like
> 
> 
> 	DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
> 	#define __FREE_ARGV	__free(argv)
> 	
> 	void func(void)
> 	{
> 		char **argv __FREE_ARGV = argv_split(...);
> 		do_something(argv);
> 		return;
> 	}
> 
> This way I can press Ctrl-] and see what the cleanup code actually does.
> Can save a second or two. Important when you try to read the code you are
> not familiar with.

Right, so I've been playing with neovim and clangd (lsp), and I'm very
disappointed to have to tell you that that also doesn't get it :-(

One thing we can and should do is something like:

diff --git a/scripts/tags.sh b/scripts/tags.sh
index b21236377998..f01d694abe65 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -212,6 +212,8 @@ regex_c=(
 	'/^SEQCOUNT_LOCKTYPE(\([^,]*\),[[:space:]]*\([^,]*\),[^)]*)/seqcount_\2_init/'
 	'/^\<DECLARE_IDTENTRY[[:alnum:]_]*([^,)]*,[[:space:]]*\([[:alnum:]_]\+\)/\1/'
 	'/^\<DEFINE_IDTENTRY[[:alnum:]_]*([[:space:]]*\([[:alnum:]_]\+\)/\1/'
+	'/^\<DEFINE_FREE(\([[:alnum:]_]\+\)/cleanup_\1/'
+	'/^\<DEFINE_CLASS(\([[:alnum:]_]\+\)/class_\1/'
 )
 regex_kconfig=(
 	'/^[[:blank:]]*\(menu\|\)config[[:blank:]]\+\([[:alnum:]_]\+\)/\2/'

That should be able to let you do: ':ts cleanup_argv'

Re: DEFINE_FREE/CLASS && code readability (Was: [PATCH v2 2/6] Provide __free(argv) for argv_split() users)

Posted by Oleg Nesterov 1 year, 1 month ago

On 01/06, Peter Zijlstra wrote:
>
> On Sun, Jan 05, 2025 at 03:14:22PM +0100, Oleg Nesterov wrote:
>
> > Perhaps we can establish a simple rule that every DEFINE_FREE() or DEFINE_CLASS()
> > should add another #define? I mean something like
> >
> > 	DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
> > 	#define __FREE_ARGV	__free(argv)
> >
> > 	void func(void)
> > 	{
> > 		char **argv __FREE_ARGV = argv_split(...);
> > 		do_something(argv);
> > 		return;
> > 	}
> >
> > This way I can press Ctrl-] and see what the cleanup code actually does.
> > Can save a second or two. Important when you try to read the code you are
> > not familiar with.
>
> Right, so I've been playing with neovim and clangd (lsp), and I'm very
> disappointed to have to tell you that that also doesn't get it :-(
>
> One thing we can and should do is something like:
>
> diff --git a/scripts/tags.sh b/scripts/tags.sh
> index b21236377998..f01d694abe65 100755
> --- a/scripts/tags.sh
> +++ b/scripts/tags.sh
> @@ -212,6 +212,8 @@ regex_c=(
>  	'/^SEQCOUNT_LOCKTYPE(\([^,]*\),[[:space:]]*\([^,]*\),[^)]*)/seqcount_\2_init/'
>  	'/^\<DECLARE_IDTENTRY[[:alnum:]_]*([^,)]*,[[:space:]]*\([[:alnum:]_]\+\)/\1/'
>  	'/^\<DEFINE_IDTENTRY[[:alnum:]_]*([[:space:]]*\([[:alnum:]_]\+\)/\1/'
> +	'/^\<DEFINE_FREE(\([[:alnum:]_]\+\)/cleanup_\1/'
> +	'/^\<DEFINE_CLASS(\([[:alnum:]_]\+\)/class_\1/'

Yes, thanks ;)

Ctrl-] still won't work, but at least ":ta cleanup_argv" will do.

Thanks,

Oleg.

Re: DEFINE_FREE/CLASS && code readability (Was: [PATCH v2 2/6] Provide __free(argv) for argv_split() users)

Posted by Peter Zijlstra 1 year, 1 month ago

On Mon, Jan 06, 2025 at 11:26:48AM +0100, Peter Zijlstra wrote:
> On Sun, Jan 05, 2025 at 03:14:22PM +0100, Oleg Nesterov wrote:
> 
> > OK, so it can be used as
> > 
> > 	void func(void)
> > 	{
> > 		char **argv __free(argv) = argv_split(...);
> > 		do_something(argv);
> > 		return;
> > 	}
> > 
> > And I cry every time when I read the code like this ;)
> > 
> > Because, to understand this code, I need to do the "nontrivial" grep to find
> > "DEFINE_FREE(argv,".
> > 
> > Perhaps we can establish a simple rule that every DEFINE_FREE() or DEFINE_CLASS()
> > should add another #define? I mean something like
> > 
> > 
> > 	DEFINE_FREE(argv, char **, if (!IS_ERR_OR_NULL(_T)) argv_free(_T))
> > 	#define __FREE_ARGV	__free(argv)
> > 	
> > 	void func(void)
> > 	{
> > 		char **argv __FREE_ARGV = argv_split(...);
> > 		do_something(argv);
> > 		return;
> > 	}
> > 
> > This way I can press Ctrl-] and see what the cleanup code actually does.
> > Can save a second or two. Important when you try to read the code you are
> > not familiar with.
> 
> Right, so I've been playing with neovim and clangd (lsp), and I'm very
> disappointed to have to tell you that that also doesn't get it :-(
> 
> One thing we can and should do is something like:
> 
> diff --git a/scripts/tags.sh b/scripts/tags.sh
> index b21236377998..f01d694abe65 100755
> --- a/scripts/tags.sh
> +++ b/scripts/tags.sh
> @@ -212,6 +212,8 @@ regex_c=(
>  	'/^SEQCOUNT_LOCKTYPE(\([^,]*\),[[:space:]]*\([^,]*\),[^)]*)/seqcount_\2_init/'
>  	'/^\<DECLARE_IDTENTRY[[:alnum:]_]*([^,)]*,[[:space:]]*\([[:alnum:]_]\+\)/\1/'
>  	'/^\<DEFINE_IDTENTRY[[:alnum:]_]*([[:space:]]*\([[:alnum:]_]\+\)/\1/'
> +	'/^\<DEFINE_FREE(\([[:alnum:]_]\+\)/cleanup_\1/'
> +	'/^\<DEFINE_CLASS(\([[:alnum:]_]\+\)/class_\1/'
	/^\<EXTEND_CLASS(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]]\+\)/class_\1\2/'
	/^\<DEFINE_GUARD(\([[:alnum:]_]\+\)/class_\1/'
	/^\<DEFINE_GUARD_COND(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]]\+\)/class_\1\2/'
	/^\<DEFINE_LOCK_GUARD_[[:digit:]](\([[:alnum:]_]\+\)/class_\1/'
	/^\<DEFINE_LOCK_GUARD_[[:digit:]]_COND(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]]\+\)/class_\1\2/'

I suppose... not tested these

[tip: locking/core] cleanup, tags: Create tags for the cleanup primitives

Posted by tip-bot2 for Peter Zijlstra 1 year, 1 month ago

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     a937f384c9da493e526ad896ef4e8054526d2941
Gitweb:        https://git.kernel.org/tip/a937f384c9da493e526ad896ef4e8054526d2941
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Mon, 06 Jan 2025 11:26:48 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 10 Jan 2025 18:16:48 +01:00

cleanup, tags: Create tags for the cleanup primitives

Oleg reported that it is hard to find the definition of things like:
__free(argv) without having to do 'git grep "DEFINE_FREE(argv,"'.

Add tag generation for the various macros in cleanup.h.

Notably 'DEFINE_FREE(argv, ...)' will now generate a 'cleanup_argv'
tag, while all the others, eg. 'DEFINE_GUARD(mutex, ...)' will
generate 'class_mutex' like tags.

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250106102647.GB20870@noisy.programming.kicks-ass.net
---
 scripts/tags.sh | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/scripts/tags.sh b/scripts/tags.sh
index b212363..7939aea 100755
--- a/scripts/tags.sh
+++ b/scripts/tags.sh
@@ -212,6 +212,13 @@ regex_c=(
 	'/^SEQCOUNT_LOCKTYPE(\([^,]*\),[[:space:]]*\([^,]*\),[^)]*)/seqcount_\2_init/'
 	'/^\<DECLARE_IDTENTRY[[:alnum:]_]*([^,)]*,[[:space:]]*\([[:alnum:]_]\+\)/\1/'
 	'/^\<DEFINE_IDTENTRY[[:alnum:]_]*([[:space:]]*\([[:alnum:]_]\+\)/\1/'
+	'/^\<DEFINE_FREE(\([[:alnum:]_]\+\)/cleanup_\1/'
+	'/^\<DEFINE_CLASS(\([[:alnum:]_]\+\)/class_\1/'
+	'/^\<EXTEND_CLASS(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]_]\+\)/class_\1\2/'
+	'/^\<DEFINE_GUARD(\([[:alnum:]_]\+\)/class_\1/'
+	'/^\<DEFINE_GUARD_COND(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]_]\+\)/class_\1\2/'
+	'/^\<DEFINE_LOCK_GUARD_[[:digit:]](\([[:alnum:]_]\+\)/class_\1/'
+	'/^\<DEFINE_LOCK_GUARD_[[:digit:]]_COND(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]_]\+\)/class_\1\2/'
 )
 regex_kconfig=(
 	'/^[[:blank:]]*\(menu\|\)config[[:blank:]]\+\([[:alnum:]_]\+\)/\2/'

Re: [tip: locking/core] cleanup, tags: Create tags for the cleanup primitives

Posted by Oleg Nesterov 1 year ago

On 01/11, tip-bot2 for Peter Zijlstra wrote:
>
> --- a/scripts/tags.sh
> +++ b/scripts/tags.sh
> @@ -212,6 +212,13 @@ regex_c=(
>  	'/^SEQCOUNT_LOCKTYPE(\([^,]*\),[[:space:]]*\([^,]*\),[^)]*)/seqcount_\2_init/'
>  	'/^\<DECLARE_IDTENTRY[[:alnum:]_]*([^,)]*,[[:space:]]*\([[:alnum:]_]\+\)/\1/'
>  	'/^\<DEFINE_IDTENTRY[[:alnum:]_]*([[:space:]]*\([[:alnum:]_]\+\)/\1/'
> +	'/^\<DEFINE_FREE(\([[:alnum:]_]\+\)/cleanup_\1/'
> +	'/^\<DEFINE_CLASS(\([[:alnum:]_]\+\)/class_\1/'
> +	'/^\<EXTEND_CLASS(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]_]\+\)/class_\1\2/'
> +	'/^\<DEFINE_GUARD(\([[:alnum:]_]\+\)/class_\1/'
> +	'/^\<DEFINE_GUARD_COND(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]_]\+\)/class_\1\2/'
> +	'/^\<DEFINE_LOCK_GUARD_[[:digit:]](\([[:alnum:]_]\+\)/class_\1/'
> +	'/^\<DEFINE_LOCK_GUARD_[[:digit:]]_COND(\([[:alnum:]_]\+\),[[:space:]]*\([[:alnum:]_]\+\)/class_\1\2/'
>  )

Thanks ;)

I don't use scripts/tags.sh, but I will add these changes to my personal
scripts.

Oleg.

[PATCH v2 1/6] tracing/kprobes: Fix to free objects when failed to copy a symbol
[PATCH v2 2/6] Provide __free(argv) for argv_split() users
[PATCH v2 3/6] tracing: Use __free() for argv in dynevent
[PATCH v2 4/6] tracing: Use __free() in trace_probe for cleanup
[PATCH v2 5/6] tracing: Use __free() for kprobe events to cleanup
[PATCH v2 6/6] tracing/kprobes: Simplify __trace_kprobe_create() by removing gotos