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Remove lock recursion for the pipe pair mutex, and disable the

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recursion on mutex initialization.

The only places where the recursive acquire is performed are read and
write filters, since knlist, which uses the pipe pair mutex as lock,
is locked when filter is called.

The recursion was added in r93296, and consistent locking for
kn_fop->f_event() introduced in r133741.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
This commit is contained in:
Konstantin Belousov 2014-11-29 17:18:20 +00:00
parent a215cdfdb0
commit 6762091ea4
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=275260
1 changed files with 3 additions and 7 deletions
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10
sys/kern/sys_pipe.c
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@ -318,7 +318,7 @@ pipe_zone_init(void *mem, int size, int flags)
pp = (struct pipepair *)mem;
mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF | MTX_RECURSE);
mtx_init(&pp->pp_mtx, "pipe mutex", NULL, MTX_DEF);
return (0);
}
@ -1792,7 +1792,7 @@ filt_piperead(struct knote *kn, long hint)
struct pipe *wpipe = rpipe->pipe_peer;
int ret;
PIPE_LOCK(rpipe);
PIPE_LOCK_ASSERT(rpipe, MA_OWNED);
kn->kn_data = rpipe->pipe_buffer.cnt;
if ((kn->kn_data == 0) && (rpipe->pipe_state & PIPE_DIRECTW))
kn->kn_data = rpipe->pipe_map.cnt;
@ -1801,11 +1801,9 @@ filt_piperead(struct knote *kn, long hint)
wpipe->pipe_present != PIPE_ACTIVE ||
(wpipe->pipe_state & PIPE_EOF)) {
kn->kn_flags |= EV_EOF;
PIPE_UNLOCK(rpipe);
return (1);
}
ret = kn->kn_data > 0;
PIPE_UNLOCK(rpipe);
return ret;
}
@ -1816,12 +1814,11 @@ filt_pipewrite(struct knote *kn, long hint)
struct pipe *wpipe;
wpipe = kn->kn_hook;
PIPE_LOCK(wpipe);
PIPE_LOCK_ASSERT(wpipe, MA_OWNED);
if (wpipe->pipe_present != PIPE_ACTIVE ||
(wpipe->pipe_state & PIPE_EOF)) {
kn->kn_data = 0;
kn->kn_flags |= EV_EOF;
PIPE_UNLOCK(wpipe);
return (1);
}
kn->kn_data = (wpipe->pipe_buffer.size > 0) ?
@ -1829,7 +1826,6 @@ filt_pipewrite(struct knote *kn, long hint)
if (wpipe->pipe_state & PIPE_DIRECTW)
kn->kn_data = 0;
PIPE_UNLOCK(wpipe);
return (kn->kn_data >= PIPE_BUF);
}