Fix spinlock_t definition without comment.
Signed-off-by: Madhumitha Prabakaran madhumithabiw@gmail.com --- drivers/staging/greybus/connection.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/greybus/connection.h b/drivers/staging/greybus/connection.h index 5ca3befc0636..0aedd246e94a 100644 --- a/drivers/staging/greybus/connection.h +++ b/drivers/staging/greybus/connection.h @@ -47,7 +47,7 @@ struct gb_connection { unsigned long flags;
struct mutex mutex; - spinlock_t lock; + spinlock_t lock; /* Protect structure fields */ enum gb_connection_state state; struct list_head operations;
On Fri, Apr 05, 2019 at 03:00:46PM -0500, Madhumitha Prabakaran wrote:
Fix spinlock_t definition without comment.
Signed-off-by: Madhumitha Prabakaran madhumithabiw@gmail.com
drivers/staging/greybus/connection.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/greybus/connection.h b/drivers/staging/greybus/connection.h index 5ca3befc0636..0aedd246e94a 100644 --- a/drivers/staging/greybus/connection.h +++ b/drivers/staging/greybus/connection.h @@ -47,7 +47,7 @@ struct gb_connection { unsigned long flags; struct mutex mutex;
- spinlock_t lock;
- spinlock_t lock; /* Protect structure fields */ enum gb_connection_state state;
What does the mutex do then? Why can't we just use the spinlock for everything?
I did glance at the code and it wasn't immediately obvious to me.
regards, dan carpenter
On 4/5/19 3:53 PM, Dan Carpenter wrote:
On Fri, Apr 05, 2019 at 03:00:46PM -0500, Madhumitha Prabakaran wrote:
Fix spinlock_t definition without comment.
Signed-off-by: Madhumitha Prabakaran madhumithabiw@gmail.com
Madhumitha, the reason one would want a comment associated with a lock field in a structure is to get some understanding of why it's needed. Saying "protect structure fields" is not enough, because that can pretty much be assumed, so a comment like that adds no value.
Looking at the code, you can see the lock field protects the connection's operations list. It also appears to be needed for accessing the state field (reading or updating).
Given that, a better comment might be:
spinlock_t lock; /* operations list and state */
--- drivers/staging/greybus/connection.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/greybus/connection.h b/drivers/staging/greybus/connection.h index 5ca3befc0636..0aedd246e94a 100644 --- a/drivers/staging/greybus/connection.h +++ b/drivers/staging/greybus/connection.h @@ -47,7 +47,7 @@ struct gb_connection { unsigned long flags;
struct mutex mutex; - spinlock_t lock; + spinlock_t lock; /* Protect structure fields */ enum gb_connection_state state;
What does the mutex do then? Why can't we just use the spinlock for everything?
The mutex needs to be held during enable and disable of a connection. Johan might be able to give you a more complete answer but these operations (or at least the enable) need to block, so can't hold a spinlock.
-Alex
I did glance at the code and it wasn't immediately obvious to me.
regards, dan carpenter
_______________________________________________ greybus-dev mailing list greybus-dev@lists.linaro.org https://lists.linaro.org/mailman/listinfo/greybus-dev
On Fri, Apr 05, 2019 at 05:50:10PM -0500, Alex Elder wrote:
On 4/5/19 3:53 PM, Dan Carpenter wrote:
On Fri, Apr 05, 2019 at 03:00:46PM -0500, Madhumitha Prabakaran wrote:
Fix spinlock_t definition without comment.
Signed-off-by: Madhumitha Prabakaran madhumithabiw@gmail.com
Madhumitha, the reason one would want a comment associated with a lock field in a structure is to get some understanding of why it's needed. Saying "protect structure fields" is not enough, because that can pretty much be assumed, so a comment like that adds no value.
That's true. It doesn't make much sense.
Looking at the code, you can see the lock field protects the connection's operations list. It also appears to be needed for accessing the state field (reading or updating).
Along with that, in some cases the spinlocks are protecting hd_links and bundle_links list.
Lines : drivers/staging/greybus/connection.c#895 #896
Given that, a better comment might be:
spinlock_t lock; /* operations list and state */--- drivers/staging/greybus/connection.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/greybus/connection.h b/drivers/staging/greybus/connection.h index 5ca3befc0636..0aedd246e94a 100644 --- a/drivers/staging/greybus/connection.h +++ b/drivers/staging/greybus/connection.h @@ -47,7 +47,7 @@ struct gb_connection { unsigned long flags;
struct mutex mutex; - spinlock_t lock; + spinlock_t lock; /* Protect structure fields */ enum gb_connection_state state;
What does the mutex do then? Why can't we just use the spinlock for everything?
The mutex needs to be held during enable and disable of a connection. Johan might be able to give you a more complete answer but these operations (or at least the enable) need to block, so can't hold a spinlock.
-Alex
Thanks for explaining it. Checking on the code, mutexes protect spinlock_t for gb_connection_state fields and gb_connection_state fields itself in struct gb_connection.
I did glance at the code and it wasn't immediately obvious to me.
regards, dan carpenter
_______________________________________________ greybus-dev mailing list greybus-dev@lists.linaro.org https://lists.linaro.org/mailman/listinfo/greybus-dev
On Fri, Apr 05, 2019 at 05:50:10PM -0500, Alex Elder wrote:
On 4/5/19 3:53 PM, Dan Carpenter wrote:
On Fri, Apr 05, 2019 at 03:00:46PM -0500, Madhumitha Prabakaran wrote:
Fix spinlock_t definition without comment.
Signed-off-by: Madhumitha Prabakaran madhumithabiw@gmail.com
Madhumitha, the reason one would want a comment associated with a lock field in a structure is to get some understanding of why it's needed. Saying "protect structure fields" is not enough, because that can pretty much be assumed, so a comment like that adds no value.
Looking at the code, you can see the lock field protects the connection's operations list. It also appears to be needed for accessing the state field (reading or updating).
Given that, a better comment might be:
spinlock_t lock; /* operations list and state */--- drivers/staging/greybus/connection.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/greybus/connection.h b/drivers/staging/greybus/connection.h index 5ca3befc0636..0aedd246e94a 100644 --- a/drivers/staging/greybus/connection.h +++ b/drivers/staging/greybus/connection.h @@ -47,7 +47,7 @@ struct gb_connection { unsigned long flags;
struct mutex mutex; - spinlock_t lock; + spinlock_t lock; /* Protect structure fields */ enum gb_connection_state state;
What does the mutex do then? Why can't we just use the spinlock for everything?
The mutex needs to be held during enable and disable of a connection. Johan might be able to give you a more complete answer but these operations (or at least the enable) need to block, so can't hold a spinlock.
Yeah, I should have documented this at the time.
You're right that the connection spinlock protects the operation list, and the mutex the connection state, but there are some other dependencies here and I don't have time to look at this at the moment.
Better to leave as is, I'd say.
Johan
On Fri, Apr 05, 2019 at 11:53:04PM +0300, Dan Carpenter wrote:
On Fri, Apr 05, 2019 at 03:00:46PM -0500, Madhumitha Prabakaran wrote:
Fix spinlock_t definition without comment.
Signed-off-by: Madhumitha Prabakaran madhumithabiw@gmail.com
drivers/staging/greybus/connection.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/greybus/connection.h b/drivers/staging/greybus/connection.h index 5ca3befc0636..0aedd246e94a 100644 --- a/drivers/staging/greybus/connection.h +++ b/drivers/staging/greybus/connection.h @@ -47,7 +47,7 @@ struct gb_connection { unsigned long flags; struct mutex mutex;
- spinlock_t lock;
- spinlock_t lock; /* Protect structure fields */ enum gb_connection_state state;
What does the mutex do then? Why can't we just use the spinlock for everything?
Here, mutexes protect spinlock_t for gb_connection_state fields and gb_connection_state fields itself in struct gb_connection.
However, I wasn't sure then and now exactly, how to find out which resources in the structure, the spinlock or mutex is performing kernel synchronization.
I did glance at the code and it wasn't immediately obvious to me.
Thanks for reviewing it.
regards, dan carpenter
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Alex Elder -
Dan Carpenter -
Johan Hovold -
Madhumitha Prabakaran -
Madhumthia Prabakaran