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[947-mt-compatibility-for-hooks] Checkpoint: hook library done, hooks to do

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This commit is contained in:
Francis Dupont
2019-11-06 14:08:26 +01:00
committed by Razvan Becheriu
parent 499e09cb45
commit f241cdd7c4
1 changed files with 31 additions and 7 deletions
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38
src/lib/hooks/hooks_user.dox
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@@ -274,15 +274,22 @@ erver multi-threading configuration. The value 0 means not compatible
and is the default when the function is not implemented. not 0 values and is the default when the function is not implemented. not 0 values
mean compatible. mean compatible.
If your code implements it and returns the value 0 it is recommended
to document the reason so someone revisiting the code will not by
accident change the code.
To be compatible means: To be compatible means:
- the code associated with DHCP packet processing callouts e.g. - the code associated with DHCP packet processing callouts e.g.
pkt4_receive or pkt6_send must be reentrant so the multi-threaded DHCP service pkt4_receive or pkt6_send must be thread safe so the multi-threaded
can simultaneously calls more than once on of these callouts. DHCP service can simultaneously calls more than once on of these callouts.
- commands a library registers must be reentrant - commands a library registers are not required to be thread safe because
- when a library implements a backend API (e.g. host data source) the service commands are executed by the main thread. Now it is a good idea to make
methods must be reentrant them thread safe and to document cases where they are not.
- (shall be modified later) a library must not modify the internal - when a library implements a thread safe backend API (e.g. host data
configuration of the server, e.g. create or delete a subnet. ource) the service methods must be thread safe.
- a library which modifies the internal configuration of the server,
e.g. create or delete a subnet, must enter a critical section using
the @c isc::dhcp::MultiThreadingCriticalSection RAII class.
In the tutoral, we'll put "multi_threading_compatible" in its own file, In the tutoral, we'll put "multi_threading_compatible" in its own file,
multi_threading_compatible.cc. The contents are: multi_threading_compatible.cc. The contents are:
@@ -299,6 +306,23 @@ int multi_threading_compatible() {
} }
@endcode @endcode
and for a command creating a new subnet:
@code
#include <dhcpsrv/multi_threading_utils.h>
int commandHandler(CalloutHandle& handle) {
...
{
// Enter the critical section.
MultiThreadingCriticalSection ct;
<add the subnet>
// Leave the critical section.
}
...
}
@endcode
@subsection hooksdgCallouts Callouts @subsection hooksdgCallouts Callouts
Having sorted out the framework, we now come to the functions that Having sorted out the framework, we now come to the functions that