Mismatched mutex_enter in tcp_input.c/syn_cache_get ?

[je]

While looking through the tcp syn cache code I noticed near the end of
syn_cache_get in tcp_input.c there is a branch of code for handling
errors that calls mutex_enter(softnet_lock), but I can't find a matching
call to mutex_exit anywhere. Is this a bug, am I not seeing the exit, or
am I not understanding the softnet_lock mutex system?

For reference, the mutex_enter call in question is on line 4242 of
tcp_input.c version 1.321.

Thanks!
John

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[Manuel Bouyer]

Post by je
While looking through the tcp syn cache code I noticed near the end
of syn_cache_get in tcp_input.c there is a branch of code for
handling errors that calls mutex_enter(softnet_lock), but I can't
find a matching call to mutex_exit anywhere. Is this a bug, am I not
seeing the exit, or am I not understanding the softnet_lock mutex
system?
For reference, the mutex_enter call in question is on line 4242 of
tcp_input.c version 1.321.

as I understand it (but I may be wrong, this code is complicated and
poorly documented), syn_cache_get() is called with softnet_lock held.
sonewconn() will allocate a new socket and its lock will be softnet_lock.
In the code you point out, soabort() will release so->so_lock, which is
softnet_lock. So softnet_lock has been released, we have to get it again.