| Message ID | 1430496088-5374-1-git-send-email-dianders@chromium.org |
|---|---|
| State | New |
| Headers | show |
On Fri, May 1, 2015 at 6:01 PM, Doug Anderson <dianders@chromium.org> wrote: > Way back, when the world was a simpler place and there was no war, no > evil, and no kernel bugs, there was just a single pinctrl lock. That > was how the world was when (57291ce pinctrl: core device tree mapping > table parsing support) was written. In that case, there were > instances where the pinctrl mutex was already held when > pinctrl_register_map() was called, hence a "locked" parameter was > passed to the function to indicate that the mutex was already locked > (so we shouldn't lock it again). > > A few years ago in (42fed7b pinctrl: move subsystem mutex to > pinctrl_dev struct), we switched to a separate pinctrl_maps_mutex. > ...but (oops) we forgot to re-think about the whole "locked" parameter > for pinctrl_register_map(). Basically the "locked" parameter appears > to still refer to whether the bigger pinctrl_dev mutex is locked, but > we're using it to skip locks of our (now separate) pinctrl_maps_mutex. > > That's kind of a bad thing(TM). Probably nobody noticed because most > of the calls to pinctrl_register_map happen at boot time and we've got > synchronous device probing. ...and even cases where we're > asynchronous don't end up actually hitting the race too often. ...but > after banging my head against the wall for a bug that reproduced 1 out > of 1000 reboots and lots of looking through kgdb, I finally noticed > this. > > Anyway, we can now safely remove the "locked" parameter and go back to > a war-free, evil-free, and kernel-bug-free world. > > Fixes: 42fed7ba44e4 ("pinctrl: move subsystem mutex to pinctrl_dev struct") > Signed-off-by: Doug Anderson <dianders@chromium.org> GOOD CATCH. Patch applied for fixes. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c index 89dca77..18ee208 100644 --- a/drivers/pinctrl/core.c +++ b/drivers/pinctrl/core.c @@ -1110,7 +1110,7 @@ void devm_pinctrl_put(struct pinctrl *p) EXPORT_SYMBOL_GPL(devm_pinctrl_put); int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps, - bool dup, bool locked) + bool dup) { int i, ret; struct pinctrl_maps *maps_node; @@ -1178,11 +1178,9 @@ int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps, maps_node->maps = maps; } - if (!locked) - mutex_lock(&pinctrl_maps_mutex); + mutex_lock(&pinctrl_maps_mutex); list_add_tail(&maps_node->node, &pinctrl_maps); - if (!locked) - mutex_unlock(&pinctrl_maps_mutex); + mutex_unlock(&pinctrl_maps_mutex); return 0; } @@ -1197,7 +1195,7 @@ int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps, int pinctrl_register_mappings(struct pinctrl_map const *maps, unsigned num_maps) { - return pinctrl_register_map(maps, num_maps, true, false); + return pinctrl_register_map(maps, num_maps, true); } void pinctrl_unregister_map(struct pinctrl_map const *map) diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h index 75476b3..b24ea84 100644 --- a/drivers/pinctrl/core.h +++ b/drivers/pinctrl/core.h @@ -183,7 +183,7 @@ static inline struct pin_desc *pin_desc_get(struct pinctrl_dev *pctldev, } int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps, - bool dup, bool locked); + bool dup); void pinctrl_unregister_map(struct pinctrl_map const *map); extern int pinctrl_force_sleep(struct pinctrl_dev *pctldev); diff --git a/drivers/pinctrl/devicetree.c b/drivers/pinctrl/devicetree.c index eda13de..0bbf7d7 100644 --- a/drivers/pinctrl/devicetree.c +++ b/drivers/pinctrl/devicetree.c @@ -92,7 +92,7 @@ static int dt_remember_or_free_map(struct pinctrl *p, const char *statename, dt_map->num_maps = num_maps; list_add_tail(&dt_map->node, &p->dt_maps); - return pinctrl_register_map(map, num_maps, false, true); + return pinctrl_register_map(map, num_maps, false); } struct pinctrl_dev *of_pinctrl_get(struct device_node *np)
Way back, when the world was a simpler place and there was no war, no evil, and no kernel bugs, there was just a single pinctrl lock. That was how the world was when (57291ce pinctrl: core device tree mapping table parsing support) was written. In that case, there were instances where the pinctrl mutex was already held when pinctrl_register_map() was called, hence a "locked" parameter was passed to the function to indicate that the mutex was already locked (so we shouldn't lock it again). A few years ago in (42fed7b pinctrl: move subsystem mutex to pinctrl_dev struct), we switched to a separate pinctrl_maps_mutex. ...but (oops) we forgot to re-think about the whole "locked" parameter for pinctrl_register_map(). Basically the "locked" parameter appears to still refer to whether the bigger pinctrl_dev mutex is locked, but we're using it to skip locks of our (now separate) pinctrl_maps_mutex. That's kind of a bad thing(TM). Probably nobody noticed because most of the calls to pinctrl_register_map happen at boot time and we've got synchronous device probing. ...and even cases where we're asynchronous don't end up actually hitting the race too often. ...but after banging my head against the wall for a bug that reproduced 1 out of 1000 reboots and lots of looking through kgdb, I finally noticed this. Anyway, we can now safely remove the "locked" parameter and go back to a war-free, evil-free, and kernel-bug-free world. Fixes: 42fed7ba44e4 ("pinctrl: move subsystem mutex to pinctrl_dev struct") Signed-off-by: Doug Anderson <dianders@chromium.org> --- drivers/pinctrl/core.c | 10 ++++------ drivers/pinctrl/core.h | 2 +- drivers/pinctrl/devicetree.c | 2 +- 3 files changed, 6 insertions(+), 8 deletions(-)