From 6ab428604f724cf217a47b7d3f3353aab815b40e Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 28 Oct 2022 10:45:44 -1000 Subject: cgroup: Implement DEBUG_CGROUP_REF It's really difficult to debug when cgroup or css refs leak. Let's add a debug option to force the refcnt function to not be inlined so that they can be kprobed for debugging. Signed-off-by: Tejun Heo --- include/linux/cgroup.h | 97 ++++++------------------------------------- include/linux/cgroup_refcnt.h | 90 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 102 insertions(+), 85 deletions(-) create mode 100644 include/linux/cgroup_refcnt.h (limited to 'include/linux') diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index a88de5bdeaa9..5c9c07a44706 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -309,71 +309,23 @@ void css_task_iter_end(struct css_task_iter *it); * Inline functions. */ +#ifdef CONFIG_DEBUG_CGROUP_REF +void css_get(struct cgroup_subsys_state *css); +void css_get_many(struct cgroup_subsys_state *css, unsigned int n); +bool css_tryget(struct cgroup_subsys_state *css); +bool css_tryget_online(struct cgroup_subsys_state *css); +void css_put(struct cgroup_subsys_state *css); +void css_put_many(struct cgroup_subsys_state *css, unsigned int n); +#else +#define CGROUP_REF_FN_ATTRS static inline +#include +#endif + static inline u64 cgroup_id(const struct cgroup *cgrp) { return cgrp->kn->id; } -/** - * css_get - obtain a reference on the specified css - * @css: target css - * - * The caller must already have a reference. - */ -static inline void css_get(struct cgroup_subsys_state *css) -{ - if (!(css->flags & CSS_NO_REF)) - percpu_ref_get(&css->refcnt); -} - -/** - * css_get_many - obtain references on the specified css - * @css: target css - * @n: number of references to get - * - * The caller must already have a reference. - */ -static inline void css_get_many(struct cgroup_subsys_state *css, unsigned int n) -{ - if (!(css->flags & CSS_NO_REF)) - percpu_ref_get_many(&css->refcnt, n); -} - -/** - * css_tryget - try to obtain a reference on the specified css - * @css: target css - * - * Obtain a reference on @css unless it already has reached zero and is - * being released. This function doesn't care whether @css is on or - * offline. The caller naturally needs to ensure that @css is accessible - * but doesn't have to be holding a reference on it - IOW, RCU protected - * access is good enough for this function. Returns %true if a reference - * count was successfully obtained; %false otherwise. - */ -static inline bool css_tryget(struct cgroup_subsys_state *css) -{ - if (!(css->flags & CSS_NO_REF)) - return percpu_ref_tryget(&css->refcnt); - return true; -} - -/** - * css_tryget_online - try to obtain a reference on the specified css if online - * @css: target css - * - * Obtain a reference on @css if it's online. The caller naturally needs - * to ensure that @css is accessible but doesn't have to be holding a - * reference on it - IOW, RCU protected access is good enough for this - * function. Returns %true if a reference count was successfully obtained; - * %false otherwise. - */ -static inline bool css_tryget_online(struct cgroup_subsys_state *css) -{ - if (!(css->flags & CSS_NO_REF)) - return percpu_ref_tryget_live(&css->refcnt); - return true; -} - /** * css_is_dying - test whether the specified css is dying * @css: target css @@ -394,31 +346,6 @@ static inline bool css_is_dying(struct cgroup_subsys_state *css) return !(css->flags & CSS_NO_REF) && percpu_ref_is_dying(&css->refcnt); } -/** - * css_put - put a css reference - * @css: target css - * - * Put a reference obtained via css_get() and css_tryget_online(). - */ -static inline void css_put(struct cgroup_subsys_state *css) -{ - if (!(css->flags & CSS_NO_REF)) - percpu_ref_put(&css->refcnt); -} - -/** - * css_put_many - put css references - * @css: target css - * @n: number of references to put - * - * Put references obtained via css_get() and css_tryget_online(). - */ -static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n) -{ - if (!(css->flags & CSS_NO_REF)) - percpu_ref_put_many(&css->refcnt, n); -} - static inline void cgroup_get(struct cgroup *cgrp) { css_get(&cgrp->self); diff --git a/include/linux/cgroup_refcnt.h b/include/linux/cgroup_refcnt.h new file mode 100644 index 000000000000..1aa89295dac0 --- /dev/null +++ b/include/linux/cgroup_refcnt.h @@ -0,0 +1,90 @@ +/** + * css_get - obtain a reference on the specified css + * @css: target css + * + * The caller must already have a reference. + */ +CGROUP_REF_FN_ATTRS +void css_get(struct cgroup_subsys_state *css) +{ + if (!(css->flags & CSS_NO_REF)) + percpu_ref_get(&css->refcnt); +} + +/** + * css_get_many - obtain references on the specified css + * @css: target css + * @n: number of references to get + * + * The caller must already have a reference. + */ +CGROUP_REF_FN_ATTRS +void css_get_many(struct cgroup_subsys_state *css, unsigned int n) +{ + if (!(css->flags & CSS_NO_REF)) + percpu_ref_get_many(&css->refcnt, n); +} + +/** + * css_tryget - try to obtain a reference on the specified css + * @css: target css + * + * Obtain a reference on @css unless it already has reached zero and is + * being released. This function doesn't care whether @css is on or + * offline. The caller naturally needs to ensure that @css is accessible + * but doesn't have to be holding a reference on it - IOW, RCU protected + * access is good enough for this function. Returns %true if a reference + * count was successfully obtained; %false otherwise. + */ +CGROUP_REF_FN_ATTRS +bool css_tryget(struct cgroup_subsys_state *css) +{ + if (!(css->flags & CSS_NO_REF)) + return percpu_ref_tryget(&css->refcnt); + return true; +} + +/** + * css_tryget_online - try to obtain a reference on the specified css if online + * @css: target css + * + * Obtain a reference on @css if it's online. The caller naturally needs + * to ensure that @css is accessible but doesn't have to be holding a + * reference on it - IOW, RCU protected access is good enough for this + * function. Returns %true if a reference count was successfully obtained; + * %false otherwise. + */ +CGROUP_REF_FN_ATTRS +bool css_tryget_online(struct cgroup_subsys_state *css) +{ + if (!(css->flags & CSS_NO_REF)) + return percpu_ref_tryget_live(&css->refcnt); + return true; +} + +/** + * css_put - put a css reference + * @css: target css + * + * Put a reference obtained via css_get() and css_tryget_online(). + */ +CGROUP_REF_FN_ATTRS +void css_put(struct cgroup_subsys_state *css) +{ + if (!(css->flags & CSS_NO_REF)) + percpu_ref_put(&css->refcnt); +} + +/** + * css_put_many - put css references + * @css: target css + * @n: number of references to put + * + * Put references obtained via css_get() and css_tryget_online(). + */ +CGROUP_REF_FN_ATTRS +void css_put_many(struct cgroup_subsys_state *css, unsigned int n) +{ + if (!(css->flags & CSS_NO_REF)) + percpu_ref_put_many(&css->refcnt, n); +} -- cgit v1.2.3 From 79a7f41f7f5ac69fd22eaf1fb3e230bea95f3399 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 31 Oct 2022 07:12:13 -1000 Subject: cgroup: cgroup refcnt functions should be exported when CONFIG_DEBUG_CGROUP_REF 6ab428604f72 ("cgroup: Implement DEBUG_CGROUP_REF") added a config option which forces cgroup refcnt functions to be not inlined so that they can be kprobed for debugging. However, it forgot export them when the config is enabled breaking modules which make use of css reference counting. Fix it by adding CGROUP_REF_EXPORT() macro to cgroup_refcnt.h which is defined to EXPORT_SYMBOL_GPL when CONFIG_DEBUG_CGROUP_REF is set. Signed-off-by: Tejun Heo Fixes: 6ab428604f72 ("cgroup: Implement DEBUG_CGROUP_REF") --- include/linux/cgroup.h | 1 + include/linux/cgroup_refcnt.h | 6 ++++++ kernel/cgroup/cgroup.c | 1 + 3 files changed, 8 insertions(+) (limited to 'include/linux') diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 5c9c07a44706..c8441090ca4c 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -318,6 +318,7 @@ void css_put(struct cgroup_subsys_state *css); void css_put_many(struct cgroup_subsys_state *css, unsigned int n); #else #define CGROUP_REF_FN_ATTRS static inline +#define CGROUP_REF_EXPORT(fn) #include #endif diff --git a/include/linux/cgroup_refcnt.h b/include/linux/cgroup_refcnt.h index 1aa89295dac0..2eea0a69ecfc 100644 --- a/include/linux/cgroup_refcnt.h +++ b/include/linux/cgroup_refcnt.h @@ -10,6 +10,7 @@ void css_get(struct cgroup_subsys_state *css) if (!(css->flags & CSS_NO_REF)) percpu_ref_get(&css->refcnt); } +CGROUP_REF_EXPORT(css_get) /** * css_get_many - obtain references on the specified css @@ -24,6 +25,7 @@ void css_get_many(struct cgroup_subsys_state *css, unsigned int n) if (!(css->flags & CSS_NO_REF)) percpu_ref_get_many(&css->refcnt, n); } +CGROUP_REF_EXPORT(css_get_many) /** * css_tryget - try to obtain a reference on the specified css @@ -43,6 +45,7 @@ bool css_tryget(struct cgroup_subsys_state *css) return percpu_ref_tryget(&css->refcnt); return true; } +CGROUP_REF_EXPORT(css_tryget) /** * css_tryget_online - try to obtain a reference on the specified css if online @@ -61,6 +64,7 @@ bool css_tryget_online(struct cgroup_subsys_state *css) return percpu_ref_tryget_live(&css->refcnt); return true; } +CGROUP_REF_EXPORT(css_tryget_online) /** * css_put - put a css reference @@ -74,6 +78,7 @@ void css_put(struct cgroup_subsys_state *css) if (!(css->flags & CSS_NO_REF)) percpu_ref_put(&css->refcnt); } +CGROUP_REF_EXPORT(css_put) /** * css_put_many - put css references @@ -88,3 +93,4 @@ void css_put_many(struct cgroup_subsys_state *css, unsigned int n) if (!(css->flags & CSS_NO_REF)) percpu_ref_put_many(&css->refcnt, n); } +CGROUP_REF_EXPORT(css_put_many) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index f786c4c973a0..f2743a476190 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -250,6 +250,7 @@ static int cgroup_addrm_files(struct cgroup_subsys_state *css, #ifdef CONFIG_DEBUG_CGROUP_REF #define CGROUP_REF_FN_ATTRS noinline +#define CGROUP_REF_EXPORT(fn) EXPORT_SYMBOL_GPL(fn); #include #endif -- cgit v1.2.3