| Message ID | 20250218005047.27258-1-richard.weiyang@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] doc/RCU/listRCU: refine example code for eliminating stale data | expand |
On Tue, Feb 18, 2025 at 12:50:47AM +0000, Wei Yang wrote: > This patch adjust the example code with following two purpose: > > * reduce the confusion on not releasing e->lock > * emphasize e is valid and not stale with e->lock held > > Signed-off-by: Wei Yang <richard.weiyang@gmail.com> > CC: Boqun Feng <boqun.feng@gmail.com> > CC: Alan Huang <mmpgouride@gmail.com> > Alan, could you take a look and if all looks reasonable to you, maybe a Reviewed-by or Acked-by? Thanks! Regards, Boqun > --- > v2: > * add the missing parameter *key > * make function return struct audit_entry > --- > Documentation/RCU/listRCU.rst | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/Documentation/RCU/listRCU.rst b/Documentation/RCU/listRCU.rst > index ed5c9d8c9afe..d8bb98623c12 100644 > --- a/Documentation/RCU/listRCU.rst > +++ b/Documentation/RCU/listRCU.rst > @@ -334,7 +334,7 @@ If the system-call audit module were to ever need to reject stale data, one way > to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to the > ``audit_entry`` structure, and modify audit_filter_task() as follows:: > > - static enum audit_state audit_filter_task(struct task_struct *tsk) > + static struct audit_entry *audit_filter_task(struct task_struct *tsk, char **key) > { > struct audit_entry *e; > enum audit_state state; > @@ -346,16 +346,18 @@ to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to > if (e->deleted) { > spin_unlock(&e->lock); > rcu_read_unlock(); > - return AUDIT_BUILD_CONTEXT; > + return NULL; > } > rcu_read_unlock(); > if (state == AUDIT_STATE_RECORD) > *key = kstrdup(e->rule.filterkey, GFP_ATOMIC); > - return state; > + /* As long as e->lock is held, e is valid and > + * its value is not stale */ > + return e; > } > } > rcu_read_unlock(); > - return AUDIT_BUILD_CONTEXT; > + return NULL; > } > > The ``audit_del_rule()`` function would need to set the ``deleted`` flag under the > -- > 2.34.1 > >
On Feb 18, 2025, at 08:50, Wei Yang <richard.weiyang@gmail.com> wrote: > > This patch adjust the example code with following two purpose: > > * reduce the confusion on not releasing e->lock > * emphasize e is valid and not stale with e->lock held > > Signed-off-by: Wei Yang <richard.weiyang@gmail.com> > CC: Boqun Feng <boqun.feng@gmail.com> > CC: Alan Huang <mmpgouride@gmail.com> > > --- > v2: > * add the missing parameter *key > * make function return struct audit_entry > --- > Documentation/RCU/listRCU.rst | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/Documentation/RCU/listRCU.rst b/Documentation/RCU/listRCU.rst > index ed5c9d8c9afe..d8bb98623c12 100644 > --- a/Documentation/RCU/listRCU.rst > +++ b/Documentation/RCU/listRCU.rst > @@ -334,7 +334,7 @@ If the system-call audit module were to ever need to reject stale data, one way > to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to the > ``audit_entry`` structure, and modify audit_filter_task() as follows:: > > - static enum audit_state audit_filter_task(struct task_struct *tsk) > + static struct audit_entry *audit_filter_task(struct task_struct *tsk, char **key) > { > struct audit_entry *e; > enum audit_state state; > @@ -346,16 +346,18 @@ to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to > if (e->deleted) { > spin_unlock(&e->lock); > rcu_read_unlock(); > - return AUDIT_BUILD_CONTEXT; > + return NULL; > } > rcu_read_unlock(); > if (state == AUDIT_STATE_RECORD) > *key = kstrdup(e->rule.filterkey, GFP_ATOMIC); > - return state; > + /* As long as e->lock is held, e is valid and > + * its value is not stale */ > + return e; > } > } > rcu_read_unlock(); > - return AUDIT_BUILD_CONTEXT; > + return NULL; > } > > The ``audit_del_rule()`` function would need to set the ``deleted`` flag under the > -- > 2.34.1 > I think it’s good enough to illustrate the intention here: Reviewed-by: Alan Huang <mmpgouride@gmail.com> Boqun, there is an unreviewed doc patch[1] that fixes the section “Using RCU hlist_nulls to protect list and objects” [1] https://lore.kernel.org/rcu/20240326124431.77430-1-mmpgouride@gmail.com/ : )
diff --git a/Documentation/RCU/listRCU.rst b/Documentation/RCU/listRCU.rst index ed5c9d8c9afe..d8bb98623c12 100644 --- a/Documentation/RCU/listRCU.rst +++ b/Documentation/RCU/listRCU.rst @@ -334,7 +334,7 @@ If the system-call audit module were to ever need to reject stale data, one way to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to the ``audit_entry`` structure, and modify audit_filter_task() as follows:: - static enum audit_state audit_filter_task(struct task_struct *tsk) + static struct audit_entry *audit_filter_task(struct task_struct *tsk, char **key) { struct audit_entry *e; enum audit_state state; @@ -346,16 +346,18 @@ to accomplish this would be to add a ``deleted`` flag and a ``lock`` spinlock to if (e->deleted) { spin_unlock(&e->lock); rcu_read_unlock(); - return AUDIT_BUILD_CONTEXT; + return NULL; } rcu_read_unlock(); if (state == AUDIT_STATE_RECORD) *key = kstrdup(e->rule.filterkey, GFP_ATOMIC); - return state; + /* As long as e->lock is held, e is valid and + * its value is not stale */ + return e; } } rcu_read_unlock(); - return AUDIT_BUILD_CONTEXT; + return NULL; } The ``audit_del_rule()`` function would need to set the ``deleted`` flag under the
This patch adjust the example code with following two purpose: * reduce the confusion on not releasing e->lock * emphasize e is valid and not stale with e->lock held Signed-off-by: Wei Yang <richard.weiyang@gmail.com> CC: Boqun Feng <boqun.feng@gmail.com> CC: Alan Huang <mmpgouride@gmail.com> --- v2: * add the missing parameter *key * make function return struct audit_entry --- Documentation/RCU/listRCU.rst | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)