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vhost: try to shrink pfdset when fdset_add fails

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fdset_add increments pfdset->num, but fdset_del doesn't decrement
pfdset->num, so if we call fdset_add then fdset_del in a loop without
calling fdset_shrink, we can easily exceed MAX_FDS with only a few
number of fds used.

So my solution is simply to call fdset_shrink in fdset_add when it
exceeds MAX_FDS.

Because fdset_shrink and fdset_add locks pfdset->fd_mutex we can't
call fdset_shrink inside fdset_add because that would cause a dead
lock, so this patch split fdset_shrink in two, fdset_shrink and
fdset_shrink_nolock.

Fixes: 59317cef24 ("vhost: allow many vhost-user ports")
Cc: stable@dpdk.org

Signed-off-by: Matthias Gatto <matthias.gatto@outscale.com>
This commit is contained in:
Matthias Gatto 2017-02-21 15:25:30 +01:00 committed by Yuanhan Liu
parent 6e2ea132ab
commit 1b815b8959
1 changed files with 16 additions and 8 deletions
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24
lib/librte_vhost/fd_man.c
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@ -65,17 +65,12 @@ fdset_move(struct fdset *pfdset, int dst, int src)
pfdset->rwfds[dst] = pfdset->rwfds[src];
}
/*
* Find deleted fd entries and remove them
*/
static void
fdset_shrink(struct fdset *pfdset)
fdset_shrink_nolock(struct fdset *pfdset)
{
int i;
int last_valid_idx = get_last_valid_idx(pfdset, pfdset->num - 1);
pthread_mutex_lock(&pfdset->fd_mutex);
for (i = 0; i < last_valid_idx; i++) {
if (pfdset->fd[i].fd != -1)
continue;
@ -84,7 +79,16 @@ fdset_shrink(struct fdset *pfdset)
last_valid_idx = get_last_valid_idx(pfdset, last_valid_idx - 1);
}
pfdset->num = last_valid_idx + 1;
}
/*
* Find deleted fd entries and remove them
*/
static void
fdset_shrink(struct fdset *pfdset)
{
pthread_mutex_lock(&pfdset->fd_mutex);
fdset_shrink_nolock(pfdset);
pthread_mutex_unlock(&pfdset->fd_mutex);
}
@ -151,8 +155,12 @@ fdset_add(struct fdset *pfdset, int fd, fd_cb rcb, fd_cb wcb, void *dat)
pthread_mutex_lock(&pfdset->fd_mutex);
i = pfdset->num < MAX_FDS ? pfdset->num++ : -1;
if (i == -1) {
pthread_mutex_unlock(&pfdset->fd_mutex);
return -2;
fdset_shrink_nolock(pfdset);
i = pfdset->num < MAX_FDS ? pfdset->num++ : -1;
if (i == -1) {
pthread_mutex_unlock(&pfdset->fd_mutex);
return -2;
}
}
fdset_add_fd(pfdset, i, fd, rcb, wcb, dat);