/*
* Similar to gettoken but we acquire a shared token instead of an exclusive
* token.
*/
void
lwkt_gettoken_shared(lwkt_token_t tok)
{
thread_t td = curthread;
lwkt_tokref_t ref;
ref = td->td_toks_stop;
KKASSERT(ref < &td->td_toks_end);
++td->td_toks_stop;
cpu_ccfence();
_lwkt_tokref_init(ref, tok, td, TOK_EXCLREQ);
#ifdef DEBUG_LOCKS
/*
* Taking a pool token in shared mode is a bad idea; other
* addresses deeper in the call stack may hash to the same pool
* token and you may end up with an exclusive-shared livelock.
* Warn in this condition.
*/
if ((tok >= &pool_tokens[0].token) &&
(tok < &pool_tokens[LWKT_NUM_POOL_TOKENS].token))
kprintf("Warning! Taking pool token %p in shared mode\n", tok);
#endif
if (_lwkt_trytokref_spin(ref, td, TOK_EXCLREQ))
return;
/*
* Give up running if we can't acquire the token right now.
*
* Since the tokref is already active the scheduler now
* takes care of acquisition, so we need only call
* lwkt_switch().
*
* Since we failed this was not a recursive token so upon
* return tr_tok->t_ref should be assigned to this specific
* ref.
*/
td->td_wmesg = tok->t_desc;
++tok->t_collisions;
logtoken(fail, ref);
td->td_toks_have = td->td_toks_stop - 1;
if (tokens_debug_output > 0) {
--tokens_debug_output;
spin_lock(&tok_debug_spin);
kprintf("Shar Token thread %p %s %s\n",
td, tok->t_desc, td->td_comm);
print_backtrace(6);
kprintf("\n");
spin_unlock(&tok_debug_spin);
}
lwkt_switch();
logtoken(succ, ref);
}
/*
* Get a serializing token. This routine can block.
*/
void
lwkt_gettoken(lwkt_token_t tok)
{
thread_t td = curthread;
lwkt_tokref_t ref;
ref = td->td_toks_stop;
KKASSERT(ref < &td->td_toks_end);
++td->td_toks_stop;
cpu_ccfence();
_lwkt_tokref_init(ref, tok, td, TOK_EXCLUSIVE|TOK_EXCLREQ);
#ifdef DEBUG_LOCKS
/*
* Taking an exclusive token after holding it shared will
* livelock. Scan for that case and assert.
*/
lwkt_tokref_t tk;
int found = 0;
for (tk = &td->td_toks_base; tk < ref; tk++) {
if (tk->tr_tok != tok)
continue;
found++;
if (tk->tr_count & TOK_EXCLUSIVE)
goto good;
}
/* We found only shared instances of this token if found >0 here */
KASSERT((found == 0), ("Token %p s/x livelock", tok));
good:
#endif
if (_lwkt_trytokref_spin(ref, td, TOK_EXCLUSIVE|TOK_EXCLREQ))
return;
/*
* Give up running if we can't acquire the token right now.
*
* Since the tokref is already active the scheduler now
* takes care of acquisition, so we need only call
* lwkt_switch().
*
* Since we failed this was not a recursive token so upon
* return tr_tok->t_ref should be assigned to this specific
* ref.
*/
td->td_wmesg = tok->t_desc;
++tok->t_collisions;
logtoken(fail, ref);
td->td_toks_have = td->td_toks_stop - 1;
lwkt_switch();
logtoken(succ, ref);
KKASSERT(tok->t_ref == ref);
}
