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Code Issues Releases Activity

Re-work the code slightly to avoid a possible livelock.

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MFC after:	2 weeks
This commit is contained in:
Doug Rabson 2008-07-23 09:18:08 +00:00
parent 8b4a2800de
commit 6dc0afa896
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=180743
1 changed files with 27 additions and 23 deletions
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50
sys/rpc/auth_unix.c
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@ -55,6 +55,7 @@ __FBSDID("$FreeBSD$");
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/pcpu.h>
#include <sys/refcount.h>
#include <sys/sx.h>
#include <sys/ucred.h>
@ -86,7 +87,7 @@ static struct auth_ops authunix_ops = {
struct audata {
TAILQ_ENTRY(audata) au_link;
TAILQ_ENTRY(audata) au_alllink;
int au_refs;
volatile u_int au_refs;
struct xucred au_xcred;
struct opaque_auth au_origcred; /* original credentials */
struct opaque_auth au_shcred; /* short hand cred */
@ -157,6 +158,7 @@ again:
sx_slock(&auth_unix_lock);
TAILQ_FOREACH(au, &auth_unix_cache[h], au_link) {
if (!memcmp(&xcr, &au->au_xcred, sizeof(xcr))) {
refcount_acquire(&au->au_refs);
if (sx_try_upgrade(&auth_unix_lock)) {
/*
* Keep auth_unix_all LRU sorted.
@ -164,16 +166,16 @@ again:
TAILQ_REMOVE(&auth_unix_all, au, au_alllink);
TAILQ_INSERT_TAIL(&auth_unix_all, au,
au_alllink);
au->au_refs++;
sx_xunlock(&auth_unix_lock);
return (au->au_auth);
} else {
sx_sunlock(&auth_unix_lock);
goto again;
}
return (au->au_auth);
}
}
sx_sunlock(&auth_unix_lock);
/*
* Allocate and set up auth handle
*/
@ -183,7 +185,7 @@ again:
auth->ah_ops = &authunix_ops;
auth->ah_private = (caddr_t)au;
auth->ah_verf = au->au_shcred = _null_auth;
au->au_refs = 1;
refcount_init(&au->au_refs, 1);
au->au_xcred = xcr;
au->au_shfaults = 0;
au->au_origcred.oa_base = NULL;
@ -210,18 +212,26 @@ again:
auth->ah_cred = au->au_origcred;
marshal_new_auth(auth);
if (sx_try_upgrade(&auth_unix_lock)) {
auth_unix_count++;
TAILQ_INSERT_TAIL(&auth_unix_cache[h], au, au_link);
TAILQ_INSERT_TAIL(&auth_unix_all, au, au_alllink);
au->au_refs++; /* one for the cache, one for user */
sx_xunlock(&auth_unix_lock);
return (auth);
} else {
sx_sunlock(&auth_unix_lock);
AUTH_DESTROY(auth);
goto again;
sx_xlock(&auth_unix_lock);
TAILQ_FOREACH(tau, &auth_unix_cache[h], au_link) {
if (!memcmp(&xcr, &tau->au_xcred, sizeof(xcr))) {
/*
* We lost a race to create the AUTH that
* matches this cred.
*/
sx_xunlock(&auth_unix_lock);
AUTH_DESTROY(auth);
goto again;
}
}
auth_unix_count++;
TAILQ_INSERT_TAIL(&auth_unix_cache[h], au, au_link);
TAILQ_INSERT_TAIL(&auth_unix_all, au, au_alllink);
refcount_acquire(&au->au_refs); /* one for the cache, one for user */
sx_xunlock(&auth_unix_lock);
return (auth);
}
/*
@ -316,16 +326,10 @@ static void
authunix_destroy(AUTH *auth)
{
struct audata *au;
int refs;
au = AUTH_PRIVATE(auth);
sx_xlock(&auth_unix_lock);
au->au_refs--;
refs = au->au_refs;
sx_xunlock(&auth_unix_lock);
if (refs > 0)
if (!refcount_release(&au->au_refs))
return;
mem_free(au->au_origcred.oa_base, au->au_origcred.oa_length);