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Index: sys/kern/kern_thread.c
===================================================================
--- sys/kern/kern_thread.c
+++ sys/kern/kern_thread.c
@@ -40,6 +40,7 @@
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
+#include <sys/bitstring.h>
#include <sys/epoch.h>
#include <sys/rangelock.h>
#include <sys/resourcevar.h>
@@ -138,9 +139,8 @@
#define TID_BUFFER_SIZE 1024
struct mtx tid_lock;
-static struct unrhdr *tid_unrhdr;
-static lwpid_t tid_buffer[TID_BUFFER_SIZE];
-static int tid_head, tid_tail;
+bitstr_t *tid_bitmap;
+
static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
static int maxthread;
@@ -163,14 +163,14 @@
{
static struct timeval lastfail;
static int curfail;
- int nthreads_new;
+ static lwpid_t trytid;
lwpid_t tid;
- nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1;
- if (nthreads_new >= maxthread - 100) {
+ mtx_lock(&tid_lock);
+ if (nthreads + 1 >= maxthread - 100) {
if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 ||
- nthreads_new >= maxthread) {
- atomic_subtract_int(&nthreads, 1);
+ nthreads + 1 >= maxthread) {
+ mtx_unlock(&tid_lock);
if (ppsratecheck(&lastfail, &curfail, 1)) {
printf("maxthread limit exceeded by uid %u "
"(pid %d); consider increasing kern.maxthread\n",
@@ -180,36 +180,40 @@
}
}
- tid = alloc_unr(tid_unrhdr);
- if (tid != -1)
- return (tid);
- mtx_lock(&tid_lock);
- if (tid_head == tid_tail) {
- mtx_unlock(&tid_lock);
- return (-1);
+ nthreads++;
+ /*
+ * It is an invariant that the bitmap is big enough to hold maxthread
+ * IDs. If we got to this point there has to be at least one free.
+ */
+ if (trytid >= maxthread)
+ trytid = 0;
+ bit_ffc_at(tid_bitmap, trytid, maxthread, &tid);
+ if (tid == -1) {
+ KASSERT(trytid != 0, ("unexpectedly ran out of IDs"));
+ trytid = 0;
+ bit_ffc_at(tid_bitmap, trytid, maxthread, &tid);
+ KASSERT(tid != -1, ("unexpectedly ran out of IDs"));
}
- tid = tid_buffer[tid_head];
- tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
+ bit_set(tid_bitmap, tid);
+ trytid++;
mtx_unlock(&tid_lock);
- return (tid);
+ return (tid + NO_PID);
}
static void
-tid_free(lwpid_t tid)
+tid_free(lwpid_t rtid)
{
- lwpid_t tmp_tid = -1;
+ lwpid_t tid;
+ KASSERT(rtid >= NO_PID,
+ ("%s: invalid tid %d\n", __func__, rtid));
+ tid = rtid - NO_PID;
mtx_lock(&tid_lock);
- if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
- tmp_tid = tid_buffer[tid_head];
- tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
- }
- tid_buffer[tid_tail] = tid;
- tid_tail = (tid_tail + 1) % TID_BUFFER_SIZE;
+ KASSERT(bit_test(tid_bitmap, tid) != 0,
+ ("thread ID %d not allocated\n", rtid));
+ bit_clear(tid_bitmap, tid);
+ nthreads--;
mtx_unlock(&tid_lock);
- if (tmp_tid != -1)
- free_unr(tid_unrhdr, tmp_tid);
- atomic_subtract_int(&nthreads, 1);
}
/*
@@ -359,12 +363,7 @@
}
mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
-
- /*
- * pid_max cannot be greater than PID_MAX.
- * leave one number for thread0.
- */
- tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
+ tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK);
flags = UMA_ZONE_NOFREE;
#ifdef __aarch64__

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