Line data    Source code

       1             : #ifndef HEADER_fd_src_disco_waker_fd_waker_h
       2             : #define HEADER_fd_src_disco_waker_fd_waker_h
       3             : 
       4             : /* The waker tile sleeps in epoll_wait(2) on behalf of every tile
       5             :    that owns kernel fds, so those tiles do not poll speculatively.
       6             : 
       7             :    At boot the launcher creates one "outer" epoll fd for the waker
       8             :    plus one "inner" epoll fd per client, at fixed inherited numbers.
       9             :    Inner fds sit in the outer set with EPOLLIN|EPOLLONESHOT.  Clients
      10             :    register sockets in their inner set (level-triggered) and touch
      11             :    the outer set only to rearm their own entry.  A ready inner fd
      12             :    wakes the outer epoll_wait.
      13             : 
      14             :    Wake protocol, per client: one fseq word, 0 idle / 1 ready.
      15             : 
      16             :      waker:   for each outer event: fd_fseq_update( word, 1UL );
      17             :               (EPOLLONESHOT: a slow client cannot wake-storm)
      18             : 
      19             :      client:  if fd_fseq_query( word )==1:
      20             :                 fd_fseq_update( word, 0UL );   clear FIRST
      21             :                 while( service_fds() );        drain to empty
      22             :                 fd_waker_client_rearm( idx );  rearm LAST
      23             :               the rearm MOD re-polls, so readiness that raced the
      24             :               drain re-fires: no lost-wake window.
      25             : 
      26             :    Inner entries must be level-triggered and drained to empty, or
      27             :    data can strand with no outer readiness. */
      28             : 
      29             : #include "../../util/fd_util_base.h"
      30             : 
      31           0 : #define FD_WAKER_OUTER_FD        (123500)
      32           0 : #define FD_WAKER_INNER_FD( idx ) (123501+(int)(idx))
      33             : 
      34           0 : #define FD_WAKER_CLIENT_MAX (16UL)
      35             : 
      36             : FD_PROTOTYPES_BEGIN
      37             : 
      38             : /* fd_waker_install creates the outer and client_cnt inner epoll fds
      39             :    at their fixed numbers and registers the inners in the outer set.
      40             :    Self-tests the kernel's nested-epoll wakeups first (broken on
      41             :    unpatched v5.5-v5.12; rejected at boot rather than losing wakes).
      42             :    Logs error and aborts on failure. */
      43             : 
      44             : void
      45             : fd_waker_install( ulong client_cnt );
      46             : 
      47             : /* fd_waker_client_rearm rearms the caller's entry in the outer
      48             :    epoll set after a drain (see wake protocol).  Logs err on
      49             :    failure. */
      50             : 
      51             : void
      52             : fd_waker_client_rearm( ulong idx );
      53             : 
      54             : FD_PROTOTYPES_END
      55             : 
      56             : #endif /* HEADER_fd_src_disco_waker_fd_waker_h */