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threads: introduce a limit for total number

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The intent is to replace the current id allocation method and a known upper
bound will be useful.

Reviewed by:	kib (previous version), markj (previous version)
Tested by:	pho
Differential Revision:	https://reviews.freebsd.org/D27100
This commit is contained in:
mjg 2020-11-09 23:04:30 +00:00
parent 5f9ca69c92
commit e34bb9169a
2 changed files with 58 additions and 9 deletions
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2
sys/kern/kern_thr.c
View File

@ -67,7 +67,7 @@ __FBSDID("$FreeBSD$");
static SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"thread allocation");
static int max_threads_per_proc = 1500;
int max_threads_per_proc = 1500;
SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_per_proc, CTLFLAG_RW,
&max_threads_per_proc, 0, "Limit on threads per proc");

65
sys/kern/kern_thread.c
View File

@ -59,6 +59,7 @@ __FBSDID("$FreeBSD$");
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
#include <sys/priv.h>
#include <security/audit/audit.h>
@ -142,6 +143,12 @@ static lwpid_t tid_buffer[TID_BUFFER_SIZE];
static int tid_head, tid_tail;
static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
static int maxthread;
SYSCTL_INT(_kern, OID_AUTO, maxthread, CTLFLAG_RDTUN,
&maxthread, 0, "Maximum number of threads");
static int nthreads;
struct tidhashhead *tidhashtbl;
u_long tidhash;
struct rwlock tidhash_lock;
@ -154,7 +161,24 @@ EVENTHANDLER_LIST_DEFINE(thread_fini);
static lwpid_t
tid_alloc(void)
{
lwpid_t tid;
static struct timeval lastfail;
static int curfail;
int nthreads_new;
lwpid_t tid;
nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1;
if (nthreads_new >= maxthread - 100) {
if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 ||
nthreads_new >= maxthread) {
atomic_subtract_int(&nthreads, 1);
if (ppsratecheck(&lastfail, &curfail, 1)) {
printf("maxthread limit exceeded by uid %u "
"(pid %d); consider increasing kern.maxthread\n",
curthread->td_ucred->cr_ruid, curproc->p_pid);
}
return (-1);
}
}
tid = alloc_unr(tid_unrhdr);
if (tid != -1)
@ -185,6 +209,7 @@ tid_free(lwpid_t tid)
mtx_unlock(&tid_lock);
if (tmp_tid != -1)
free_unr(tid_unrhdr, tmp_tid);
atomic_subtract_int(&nthreads, 1);
}
/*
@ -199,8 +224,6 @@ thread_ctor(void *mem, int size, void *arg, int flags)
td->td_state = TDS_INACTIVE;
td->td_lastcpu = td->td_oncpu = NOCPU;
td->td_tid = tid_alloc();
/*
* Note that td_critnest begins life as 1 because the thread is not
* running and is thereby implicitly waiting to be on the receiving
@ -208,7 +231,6 @@ thread_ctor(void *mem, int size, void *arg, int flags)
*/
td->td_critnest = 1;
td->td_lend_user_pri = PRI_MAX;
EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
#ifdef AUDIT
audit_thread_alloc(td);
#endif
@ -253,9 +275,6 @@ thread_dtor(void *mem, int size, void *arg)
osd_thread_exit(td);
td_softdep_cleanup(td);
MPASS(td->td_su == NULL);
EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
tid_free(td->td_tid);
}
/*
@ -325,6 +344,8 @@ proc_linkup(struct proc *p, struct thread *td)
thread_link(td, p);
}
extern int max_threads_per_proc;
/*
* Initialize global thread allocation resources.
*/
@ -333,6 +354,22 @@ threadinit(void)
{
uint32_t flags;
/*
* Place an upper limit on threads which can be allocated.
*
* Note that other factors may make the de facto limit much lower.
*
* Platform limits are somewhat arbitrary but deemed "more than good
* enough" for the foreseable future.
*/
if (maxthread == 0) {
#ifdef _LP64
maxthread = MIN(maxproc * max_threads_per_proc, 1000000);
#else
maxthread = MIN(maxproc * max_threads_per_proc, 100000);
#endif
}
mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
/*
@ -415,16 +452,25 @@ struct thread *
thread_alloc(int pages)
{
struct thread *td;
lwpid_t tid;
thread_reap(); /* check if any zombies to get */
td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
tid = tid_alloc();
if (tid == -1) {
return (NULL);
}
td = uma_zalloc(thread_zone, M_WAITOK);
KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
if (!vm_thread_new(td, pages)) {
uma_zfree(thread_zone, td);
tid_free(tid);
return (NULL);
}
td->td_tid = tid;
cpu_thread_alloc(td);
EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
return (td);
}
@ -447,6 +493,7 @@ void
thread_free(struct thread *td)
{
EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
lock_profile_thread_exit(td);
if (td->td_cpuset)
cpuset_rel(td->td_cpuset);
@ -455,6 +502,8 @@ thread_free(struct thread *td)
if (td->td_kstack != 0)
vm_thread_dispose(td);
callout_drain(&td->td_slpcallout);
tid_free(td->td_tid);
td->td_tid = -1;
uma_zfree(thread_zone, td);
}