| Message ID | 20240411180256.61001-1-romeusmeister@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | sysrq: Auto release device node using __free attribute | expand |
On Thu, Apr 11, 2024 at 08:02:56PM +0200, Roman Storozhenko wrote: > Add a cleanup function attribute '__free(device_node)' to the device node > pointer initialization statement and remove the pairing cleanup function > call of 'of_node_put' at the end of the function. > The '_free()' attrubute is introduced by scope-based resource management > in-kernel framework implemented in 'cleanup.h'. A pointer marked with > '__free()' attribute makes a compiler insert a cleanup function call > to the places where the pointer goes out of the scope. This feature > allows to get rid of manual cleanup function calls. > > Suggested-by: Julia.Lawall <Julia.Lawall@inria.fr> > Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com> > --- > This patch targets the next tree: > tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > tag: next-20240411 > --- > drivers/tty/sysrq.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > index 02217e3c916b..1d1261f618c0 100644 > --- a/drivers/tty/sysrq.c > +++ b/drivers/tty/sysrq.c > @@ -758,11 +758,12 @@ static void sysrq_detect_reset_sequence(struct sysrq_state *state, > static void sysrq_of_get_keyreset_config(void) > { > u32 key; > - struct device_node *np; > struct property *prop; > const __be32 *p; > > - np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > + struct device_node *np __free(device_node) = > + of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > + Did you run this through checkpatch.pl? Please do so.
On Thu, 11 Apr 2024, Greg KH wrote: > On Thu, Apr 11, 2024 at 08:02:56PM +0200, Roman Storozhenko wrote: > > Add a cleanup function attribute '__free(device_node)' to the device node > > pointer initialization statement and remove the pairing cleanup function > > call of 'of_node_put' at the end of the function. > > The '_free()' attrubute is introduced by scope-based resource management > > in-kernel framework implemented in 'cleanup.h'. A pointer marked with > > '__free()' attribute makes a compiler insert a cleanup function call > > to the places where the pointer goes out of the scope. This feature > > allows to get rid of manual cleanup function calls. > > > > Suggested-by: Julia.Lawall <Julia.Lawall@inria.fr> > > Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com> > > --- > > This patch targets the next tree: > > tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > tag: next-20240411 > > --- > > drivers/tty/sysrq.c | 7 +++---- > > 1 file changed, 3 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > > index 02217e3c916b..1d1261f618c0 100644 > > --- a/drivers/tty/sysrq.c > > +++ b/drivers/tty/sysrq.c > > @@ -758,11 +758,12 @@ static void sysrq_detect_reset_sequence(struct sysrq_state *state, > > static void sysrq_of_get_keyreset_config(void) > > { > > u32 key; > > - struct device_node *np; > > struct property *prop; > > const __be32 *p; > > > > - np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > > + struct device_node *np __free(device_node) = > > + of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > > + > > if (!np) { > > pr_debug("No sysrq node found"); > > return; > > @@ -781,8 +782,6 @@ static void sysrq_of_get_keyreset_config(void) > > > > /* Get reset timeout if any. */ > > of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); > > - > > - of_node_put(np); > > } > > #else > > static void sysrq_of_get_keyreset_config(void) > > Also, this change really makes no sense at all, the pointer never goes > out of scope except when the function is over, at the bottom. So why > make this complex change at all for no benefit? > > In other words, properly understand the change you are making and only > make it if it actually makes sense. It does not make any sense here, > right? Maybe it would be nice to get rid of of_node_puts in the general case? Even though this one is not very annoying, there are some other functions where there are many of_node_puts, and convoluted error handling code to incorporate them on both the success and failure path. So maybe it would be better to avoid the situation of having them sometimes and not having them other times? But this is an opinion, and if the general consensus is to only get rid of the cases that currently add complexity, then that is possible too. julia
This change allows us to put this pointer under automatic scope management and get rid of node_put. Besides, if a new code path is introduced we won't need to add a new of_node_put. Thanks, Roman On Thu, Apr 11, 2024 at 8:11 PM Greg KH <gregkh@linuxfoundation.org> wrote: > > On Thu, Apr 11, 2024 at 08:02:56PM +0200, Roman Storozhenko wrote: > > Add a cleanup function attribute '__free(device_node)' to the device node > > pointer initialization statement and remove the pairing cleanup function > > call of 'of_node_put' at the end of the function. > > The '_free()' attrubute is introduced by scope-based resource management > > in-kernel framework implemented in 'cleanup.h'. A pointer marked with > > '__free()' attribute makes a compiler insert a cleanup function call > > to the places where the pointer goes out of the scope. This feature > > allows to get rid of manual cleanup function calls. > > > > Suggested-by: Julia.Lawall <Julia.Lawall@inria.fr> > > Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com> > > --- > > This patch targets the next tree: > > tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > tag: next-20240411 > > --- > > drivers/tty/sysrq.c | 7 +++---- > > 1 file changed, 3 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > > index 02217e3c916b..1d1261f618c0 100644 > > --- a/drivers/tty/sysrq.c > > +++ b/drivers/tty/sysrq.c > > @@ -758,11 +758,12 @@ static void sysrq_detect_reset_sequence(struct sysrq_state *state, > > static void sysrq_of_get_keyreset_config(void) > > { > > u32 key; > > - struct device_node *np; > > struct property *prop; > > const __be32 *p; > > > > - np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > > + struct device_node *np __free(device_node) = > > + of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > > + > > if (!np) { > > pr_debug("No sysrq node found"); > > return; > > @@ -781,8 +782,6 @@ static void sysrq_of_get_keyreset_config(void) > > > > /* Get reset timeout if any. */ > > of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); > > - > > - of_node_put(np); > > } > > #else > > static void sysrq_of_get_keyreset_config(void) > > Also, this change really makes no sense at all, the pointer never goes > out of scope except when the function is over, at the bottom. So why > make this complex change at all for no benefit? > > In other words, properly understand the change you are making and only > make it if it actually makes sense. It does not make any sense here, > right? > > thanks, > > greg k-h
A: http://en.wikipedia.org/wiki/Top_post Q: Were do I find info about this thing called top-posting? A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? A: No. Q: Should I include quotations after my reply? http://daringfireball.net/2007/07/on_top On Thu, Apr 11, 2024 at 08:28:17PM +0200, Roman Storozhenko wrote: > This change allows us to put this pointer under automatic scope > management and get rid of node_put. Besides, if a new code path is > introduced we won't need to add a new of_node_put. We worry about future stuff then, in the future. So no need for changing code today for things that are not present at all, otherwise you would never be finished with anything, right? Don't make things more complex when it is not needed. Only add complexity when it is needed. thanks, greg k-h
On Thu, Apr 11, 2024 at 08:17:07PM +0200, Julia Lawall wrote: > > > On Thu, 11 Apr 2024, Greg KH wrote: > > > On Thu, Apr 11, 2024 at 08:02:56PM +0200, Roman Storozhenko wrote: > > > Add a cleanup function attribute '__free(device_node)' to the device node > > > pointer initialization statement and remove the pairing cleanup function > > > call of 'of_node_put' at the end of the function. > > > The '_free()' attrubute is introduced by scope-based resource management > > > in-kernel framework implemented in 'cleanup.h'. A pointer marked with > > > '__free()' attribute makes a compiler insert a cleanup function call > > > to the places where the pointer goes out of the scope. This feature > > > allows to get rid of manual cleanup function calls. > > > > > > Suggested-by: Julia.Lawall <Julia.Lawall@inria.fr> > > > Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com> > > > --- > > > This patch targets the next tree: > > > tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > > tag: next-20240411 > > > --- > > > drivers/tty/sysrq.c | 7 +++---- > > > 1 file changed, 3 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > > > index 02217e3c916b..1d1261f618c0 100644 > > > --- a/drivers/tty/sysrq.c > > > +++ b/drivers/tty/sysrq.c > > > @@ -758,11 +758,12 @@ static void sysrq_detect_reset_sequence(struct sysrq_state *state, > > > static void sysrq_of_get_keyreset_config(void) > > > { > > > u32 key; > > > - struct device_node *np; > > > struct property *prop; > > > const __be32 *p; > > > > > > - np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > > > + struct device_node *np __free(device_node) = > > > + of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > > > + > > > if (!np) { > > > pr_debug("No sysrq node found"); > > > return; > > > @@ -781,8 +782,6 @@ static void sysrq_of_get_keyreset_config(void) > > > > > > /* Get reset timeout if any. */ > > > of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); > > > - > > > - of_node_put(np); > > > } > > > #else > > > static void sysrq_of_get_keyreset_config(void) > > > > Also, this change really makes no sense at all, the pointer never goes > > out of scope except when the function is over, at the bottom. So why > > make this complex change at all for no benefit? > > > > In other words, properly understand the change you are making and only > > make it if it actually makes sense. It does not make any sense here, > > right? > > Maybe it would be nice to get rid of of_node_puts in the general case? That's a call for the of maintainer to make, and then if so, to do it across the whole tree, right? > Even though this one is not very annoying, there are some other functions > where there are many of_node_puts, and convoluted error handling code to > incorporate them on both the success and failure path. So maybe it would > be better to avoid the situation of having them sometimes and not having > them other times? But this is an opinion, and if the general consensus is > to only get rid of the cases that currently add complexity, then that is > possible too. Let's keep things simple until it has to be complex please. thanks, greg k-h
On Fri, 12 Apr 2024, Greg KH wrote: > On Thu, Apr 11, 2024 at 08:17:07PM +0200, Julia Lawall wrote: > > > > > > On Thu, 11 Apr 2024, Greg KH wrote: > > > > > On Thu, Apr 11, 2024 at 08:02:56PM +0200, Roman Storozhenko wrote: > > > > Add a cleanup function attribute '__free(device_node)' to the device node > > > > pointer initialization statement and remove the pairing cleanup function > > > > call of 'of_node_put' at the end of the function. > > > > The '_free()' attrubute is introduced by scope-based resource management > > > > in-kernel framework implemented in 'cleanup.h'. A pointer marked with > > > > '__free()' attribute makes a compiler insert a cleanup function call > > > > to the places where the pointer goes out of the scope. This feature > > > > allows to get rid of manual cleanup function calls. > > > > > > > > Suggested-by: Julia.Lawall <Julia.Lawall@inria.fr> > > > > Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com> > > > > --- > > > > This patch targets the next tree: > > > > tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > > > tag: next-20240411 > > > > --- > > > > drivers/tty/sysrq.c | 7 +++---- > > > > 1 file changed, 3 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > > > > index 02217e3c916b..1d1261f618c0 100644 > > > > --- a/drivers/tty/sysrq.c > > > > +++ b/drivers/tty/sysrq.c > > > > @@ -758,11 +758,12 @@ static void sysrq_detect_reset_sequence(struct sysrq_state *state, > > > > static void sysrq_of_get_keyreset_config(void) > > > > { > > > > u32 key; > > > > - struct device_node *np; > > > > struct property *prop; > > > > const __be32 *p; > > > > > > > > - np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > > > > + struct device_node *np __free(device_node) = > > > > + of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); > > > > + > > > > if (!np) { > > > > pr_debug("No sysrq node found"); > > > > return; > > > > @@ -781,8 +782,6 @@ static void sysrq_of_get_keyreset_config(void) > > > > > > > > /* Get reset timeout if any. */ > > > > of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); > > > > - > > > > - of_node_put(np); > > > > } > > > > #else > > > > static void sysrq_of_get_keyreset_config(void) > > > > > > Also, this change really makes no sense at all, the pointer never goes > > > out of scope except when the function is over, at the bottom. So why > > > make this complex change at all for no benefit? > > > > > > In other words, properly understand the change you are making and only > > > make it if it actually makes sense. It does not make any sense here, > > > right? > > > > Maybe it would be nice to get rid of of_node_puts in the general case? > > That's a call for the of maintainer to make, and then if so, to do it > across the whole tree, right? > > > Even though this one is not very annoying, there are some other functions > > where there are many of_node_puts, and convoluted error handling code to > > incorporate them on both the success and failure path. So maybe it would > > be better to avoid the situation of having them sometimes and not having > > them other times? But this is an opinion, and if the general consensus is > > to only get rid of the cases that currently add complexity, then that is > > possible too. > > Let's keep things simple until it has to be complex please. Jonathan Cameron pointed me to the following series from Rob Herring: https://lore.kernel.org/linux-devicetree/20240409-dt-cleanup-free-v2-0-5b419a4af38d@kernel.org/ The patch for of_node_put is: https://lore.kernel.org/linux-devicetree/20240409-dt-cleanup-free-v2-3-5b419a4af38d@kernel.org/ It uses __free directy. The cases in the file drivers/of/property.c have quite simple structure, with for each get just one put at the end of the scope in most cases. julia > > thanks, > > greg k-h >
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 02217e3c916b..1d1261f618c0 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -758,11 +758,12 @@ static void sysrq_detect_reset_sequence(struct sysrq_state *state, static void sysrq_of_get_keyreset_config(void) { u32 key; - struct device_node *np; struct property *prop; const __be32 *p; - np = of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); + struct device_node *np __free(device_node) = + of_find_node_by_path("/chosen/linux,sysrq-reset-seq"); + if (!np) { pr_debug("No sysrq node found"); return; @@ -781,8 +782,6 @@ static void sysrq_of_get_keyreset_config(void) /* Get reset timeout if any. */ of_property_read_u32(np, "timeout-ms", &sysrq_reset_downtime_ms); - - of_node_put(np); } #else static void sysrq_of_get_keyreset_config(void)
Add a cleanup function attribute '__free(device_node)' to the device node pointer initialization statement and remove the pairing cleanup function call of 'of_node_put' at the end of the function. The '_free()' attrubute is introduced by scope-based resource management in-kernel framework implemented in 'cleanup.h'. A pointer marked with '__free()' attribute makes a compiler insert a cleanup function call to the places where the pointer goes out of the scope. This feature allows to get rid of manual cleanup function calls. Suggested-by: Julia.Lawall <Julia.Lawall@inria.fr> Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com> --- This patch targets the next tree: tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git tag: next-20240411 --- drivers/tty/sysrq.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)