[PATCH 20/38] Add a hook for a provider-specific "update" function

[eugene.loh@oracle.com]

From: Eugene Loh <eugene.loh@oracle.com>

For up-coming USDT-probe support, we need to update a BPF map
-- at least when the dtrace session starts but possibly also later
to support systemwide USDT tracing for processes that may start up
later.

One way to do this is with a USDT-specific update function.

For now, let's add a hook for providers to have provider-specific
update functions.  User space can either call

    for (i = 0; i < ARRAY_SIZE(dt_providers); i++) {
        if (dt_providers[i]->update)
            dt_providers[i]->update(...);
    }

any time it likes.  Or it can call dt_usdt.update(...).

This is for WIP.  A different approach can be adopted later instead.

Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
---
 libdtrace/dt_provider.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libdtrace/dt_provider.h b/libdtrace/dt_provider.h
index b1b1b1b8..71b5a3c4 100644
--- a/libdtrace/dt_provider.h
+++ b/libdtrace/dt_provider.h
@@ -71,6 +71,8 @@ typedef struct dt_provimpl {
 			      void *datap);
 	void (*destroy)(dtrace_hdl_t *dtp,	/* free provider data */
 			      void *datap);
+	void (*update)(dtrace_hdl_t *dtp,	/* update provider-specific info */
+			      void *datap);
 } dt_provimpl_t;
 
 /* list dt_dtrace first */
-- 
2.18.4