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lxccontainer: lxc_container_{get,put}()

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Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Christian Brauner 2018-02-24 15:15:54 +01:00
parent 70849dc234
commit 045552aabe
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GPG Key ID: 8EB056D53EECB12D
1 changed files with 20 additions and 13 deletions
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33
src/lxc/lxccontainer.c
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@ -281,19 +281,21 @@ static void lxc_container_free(struct lxc_container *c)
free(c);
}
/*
* Consider the following case:
freer | racing get()er
==================================================================
lxc_container_put() | lxc_container_get()
\ lxclock(c->privlock) | c->numthreads < 1? (no)
\ c->numthreads = 0 | \ lxclock(c->privlock) -> waits
\ lxcunlock() | \
\ lxc_container_free() | \ lxclock() returns
| \ c->numthreads < 1 -> return 0
\ \ (free stuff) |
\ \ sem_destroy(privlock) |
/* Consider the following case:
*
* |====================================================================|
* | freer | racing get()er |
* |====================================================================|
* | lxc_container_put() | lxc_container_get() |
* | \ lxclock(c->privlock) | c->numthreads < 1? (no) |
* | \ c->numthreads = 0 | \ lxclock(c->privlock) -> waits |
* | \ lxcunlock() | \ |
* | \ lxc_container_free() | \ lxclock() returns |
* | | \ c->numthreads < 1 -> return 0 |
* | \ \ (free stuff) | |
* | \ \ sem_destroy(privlock) | |
* |_______________________________|____________________________________|
*
* When the get()er checks numthreads the first time, one of the following
* is true:
* 1. freer has set numthreads = 0. get() returns 0
@ -326,6 +328,7 @@ int lxc_container_get(struct lxc_container *c)
c->numthreads++;
container_mem_unlock(c);
return 1;
}
@ -333,14 +336,18 @@ int lxc_container_put(struct lxc_container *c)
{
if (!c)
return -1;
if (container_mem_lock(c))
return -1;
if (--c->numthreads < 1) {
container_mem_unlock(c);
lxc_container_free(c);
return 1;
}
container_mem_unlock(c);
return 0;
}