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D43488.id132906.diff
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diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -40,7 +40,7 @@
#include <sys/param.h>
#include <sys/systm.h>
-#include <sys/bitstring.h>
+#include <sys/bitset.h>
#include <sys/sysproto.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
@@ -238,10 +238,7 @@
sysctl_kern_randompid, "I",
"Random PID modulus. Special values: 0: disable, 1: choose random value");
-extern bitstr_t proc_id_pidmap;
-extern bitstr_t proc_id_grpidmap;
-extern bitstr_t proc_id_sessidmap;
-extern bitstr_t proc_id_reapmap;
+extern struct proc_id_map proc_id_pidmap;
/*
* Find an unused process ID
@@ -253,18 +250,14 @@
fork_findpid(int flags)
{
pid_t result;
- int trypid, random;
+ int _lastpid, random, trypid;
- /*
- * Avoid calling arc4random with procid_lock held.
- */
random = 0;
if (__predict_false(randompid))
random = arc4random() % randompid;
- mtx_lock(&procid_lock);
-
- trypid = lastpid + 1;
+ _lastpid = lastpid;
+ trypid = _lastpid;
if (flags & RFHIGHPID) {
if (trypid < 10)
trypid = 10;
@@ -275,27 +268,37 @@
if (trypid >= pid_max)
trypid = 2;
- bit_ffc_at(&proc_id_pidmap, trypid, pid_max, &result);
+ result = BIT_FFC_AT(pid_max, &proc_id_pidmap, trypid + 1) - 1;
if (result == -1) {
KASSERT(trypid != 2, ("unexpectedly ran out of IDs"));
trypid = 2;
goto retry;
- }
- if (bit_test(&proc_id_grpidmap, result) ||
- bit_test(&proc_id_sessidmap, result) ||
- bit_test(&proc_id_reapmap, result)) {
- trypid = result + 1;
- goto retry;
+ } else {
+ /*
+ * We try to reserve the PID first. If we were able to do that,
+ * we still need to check if the PID is not set on the other
+ * bitmaps. We assume that because we were able reserve the PID,
+ * this bit cannot be set in the other bitmaps anymore.
+ * It was either set before or it is not set.
+ */
+ if (proc_id_set_cond(PROC_ID_PID, result)) {
+ /* Lost the race. */
+ trypid = result + 1;
+ goto retry;
+ } else if (proc_id_test(PROC_ID_GROUP, result) ||
+ proc_id_test(PROC_ID_SESSION, result) ||
+ proc_id_test(PROC_ID_REAP, result)) {
+ proc_id_clear(PROC_ID_PID, result);
+ trypid = result + 1;
+ goto retry;
+ }
}
/*
* RFHIGHPID does not mess with the lastpid counter during boot.
*/
if ((flags & RFHIGHPID) == 0)
- lastpid = result;
-
- bit_set(&proc_id_pidmap, result);
- mtx_unlock(&procid_lock);
+ atomic_cmpset_acq_int(&lastpid, _lastpid, result);
return (result);
}
@@ -652,7 +655,7 @@
LIST_INSERT_HEAD(&p2->p_reaper->p_reaplist, p2, p_reapsibling);
if (p2->p_reaper == p1 && p1 != initproc) {
p2->p_reapsubtree = p2->p_pid;
- proc_id_set_cond(PROC_ID_REAP, p2->p_pid);
+ (void)proc_id_set_cond(PROC_ID_REAP, p2->p_pid);
}
sx_xunlock(&proctree_lock);
diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -37,7 +37,7 @@
#include <sys/param.h>
#include <sys/systm.h>
-#include <sys/bitstring.h>
+#include <sys/bitset.h>
#include <sys/elf.h>
#include <sys/eventhandler.h>
#include <sys/exec.h>
@@ -130,7 +130,6 @@
struct sx __exclusive_cache_line allproc_lock;
struct sx __exclusive_cache_line proctree_lock;
struct mtx __exclusive_cache_line ppeers_lock;
-struct mtx __exclusive_cache_line procid_lock;
uma_zone_t proc_zone;
uma_zone_t pgrp_zone;
@@ -183,7 +182,6 @@
sx_init(&allproc_lock, "allproc");
sx_init(&proctree_lock, "proctree");
mtx_init(&ppeers_lock, "p_peers", NULL, MTX_DEF);
- mtx_init(&procid_lock, "procid", NULL, MTX_DEF);
pidhashtbl = hashinit(maxproc / 4, M_PROC, &pidhash);
pidhashlock = (pidhash + 1) / 64;
if (pidhashlock > 0)
@@ -317,16 +315,16 @@
*
* These bitmaps are used by fork_findpid.
*/
-bitstr_t bit_decl(proc_id_pidmap, PID_MAX);
-bitstr_t bit_decl(proc_id_grpidmap, PID_MAX);
-bitstr_t bit_decl(proc_id_sessidmap, PID_MAX);
-bitstr_t bit_decl(proc_id_reapmap, PID_MAX);
-
-static bitstr_t *proc_id_array[] = {
- proc_id_pidmap,
- proc_id_grpidmap,
- proc_id_sessidmap,
- proc_id_reapmap,
+struct proc_id_map proc_id_pidmap;
+struct proc_id_map proc_id_grpidmap;
+struct proc_id_map proc_id_sessidmap;
+struct proc_id_map proc_id_reapmap;
+
+static struct proc_id_map *proc_id_array[] = {
+ &proc_id_pidmap,
+ &proc_id_grpidmap,
+ &proc_id_sessidmap,
+ &proc_id_reapmap,
};
void
@@ -335,24 +333,18 @@
KASSERT(type >= 0 && type < nitems(proc_id_array),
("invalid type %d\n", type));
- mtx_lock(&procid_lock);
- KASSERT(bit_test(proc_id_array[type], id) == 0,
- ("bit %d already set in %d\n", id, type));
- bit_set(proc_id_array[type], id);
- mtx_unlock(&procid_lock);
+ if (__predict_false(BIT_TEST_SET_ATOMIC(PID_MAX, id, proc_id_array[type]))) {
+ panic("%s: bit %d already set in %d", __func__, id, type);
+ }
}
-void
+bool
proc_id_set_cond(int type, pid_t id)
{
KASSERT(type >= 0 && type < nitems(proc_id_array),
("invalid type %d\n", type));
- if (bit_test(proc_id_array[type], id))
- return;
- mtx_lock(&procid_lock);
- bit_set(proc_id_array[type], id);
- mtx_unlock(&procid_lock);
+ return (BIT_TEST_SET_ATOMIC(PID_MAX, id, proc_id_array[type]));
}
void
@@ -361,11 +353,18 @@
KASSERT(type >= 0 && type < nitems(proc_id_array),
("invalid type %d\n", type));
- mtx_lock(&procid_lock);
- KASSERT(bit_test(proc_id_array[type], id) != 0,
- ("bit %d not set in %d\n", id, type));
- bit_clear(proc_id_array[type], id);
- mtx_unlock(&procid_lock);
+ if (__predict_false(!BIT_TEST_CLR_ATOMIC(PID_MAX, id, proc_id_array[type]))) {
+ panic("%s: bit %d not set in %d", __func__, id, type);
+ }
+}
+
+bool
+proc_id_test(int type, pid_t id)
+{
+
+ KASSERT(type >= 0 && type < nitems(proc_id_array),
+ ("invalid type %d\n", type));
+ return (BIT_ISSET_ATOMIC(PID_MAX, id, proc_id_array[type]));
}
/*
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -37,6 +37,7 @@
#ifndef _SYS_PROC_H_
#define _SYS_PROC_H_
+#include <sys/bitset.h>
#include <sys/callout.h> /* For struct callout. */
#include <sys/event.h> /* For struct klist. */
#ifdef _KERNEL
@@ -1098,7 +1099,6 @@
extern int allproc_gen;
extern struct sx proctree_lock;
extern struct mtx ppeers_lock;
-extern struct mtx procid_lock;
extern struct proc proc0; /* Process slot for swapper. */
extern struct thread0_storage thread0_st; /* Primary thread in proc0. */
#define thread0 (thread0_st.t0st_thread)
@@ -1351,9 +1351,12 @@
#define PROC_ID_SESSION 2
#define PROC_ID_REAP 3
+BITSET_DEFINE(proc_id_map, PID_MAX);
+
void proc_id_set(int type, pid_t id);
-void proc_id_set_cond(int type, pid_t id);
+bool proc_id_set_cond(int type, pid_t id);
void proc_id_clear(int type, pid_t id);
+bool proc_id_test(int type, pid_t id);
EVENTHANDLER_LIST_DECLARE(process_ctor);
EVENTHANDLER_LIST_DECLARE(process_dtor);

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