Obviously if it mm->count need to be an atomic_t, we strictly _need_ also
my new mm_lock spinlock in 2.2.1.
So you don't buy my code, but now, I don't buy both all /proc mmget/mmput
sutff and the mm->count atomic_t.
I also avoided all the mmget/mmput stuff in /proc since it _has_ to run
just serialized by the mmget/mmput semaphore (otherwise we need
my mm_lock).
I also removed the semaphore stuff because it seems to me (and to you btw
;) that _all_ places in the mm that does a down(current->mm->mmap_sem),
does always then a lock_kernel().
I also removed all the memcpy, we only need the read_lock(tasklist_lock)
held in SMP because otherwise wait4() could remove the stack of the
process under our eyes as just pointed out in the last email.
Not doing in 2.2.1 the mm->count s/atomic_t/int/ due worry of races will
mean that array.c in 2.2.1 will be not safe enough without my mm_lock
spinlock. Do you understand my point?
I rediffed everything against clean 2.2.0, and I am now running it without
any problem, seems rock solid from a /proc race point of view.
Index: arch/i386/kernel/ldt.c
===================================================================
RCS file: /var/cvs/linux/arch/i386/kernel/ldt.c,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 ldt.c
--- ldt.c 1999/01/18 01:28:57 1.1.1.1
+++ ldt.c 1999/01/27 20:09:21
@@ -83,7 +83,7 @@
set_ldt_desc(i, ldt, LDT_ENTRIES);
current->tss.ldt = _LDT(i);
load_ldt(i);
- if (atomic_read(&mm->count) > 1)
+ if (mm->count > 1)
printk(KERN_WARNING
"LDT allocated for cloned task!\n");
} else {
Index: fs/binfmt_aout.c
===================================================================
RCS file: /var/cvs/linux/fs/binfmt_aout.c,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 binfmt_aout.c
--- binfmt_aout.c 1999/01/18 01:26:49 1.1.1.1
+++ binfmt_aout.c 1999/01/27 20:09:21
@@ -101,7 +101,7 @@
# define START_STACK(u) (u.start_stack)
#endif
- if (!current->dumpable || atomic_read(¤t->mm->count) != 1)
+ if (!current->dumpable || current->mm->count != 1)
return 0;
current->dumpable = 0;
Index: fs/binfmt_elf.c
===================================================================
RCS file: /var/cvs/linux/fs/binfmt_elf.c,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 binfmt_elf.c
--- binfmt_elf.c 1999/01/18 01:26:49 1.1.1.1
+++ binfmt_elf.c 1999/01/27 20:09:21
@@ -1067,7 +1067,7 @@
if (!current->dumpable ||
limit < ELF_EXEC_PAGESIZE ||
- atomic_read(¤t->mm->count) != 1)
+ current->mm->count != 1)
return 0;
current->dumpable = 0;
Index: fs/exec.c
===================================================================
RCS file: /var/cvs/linux/fs/exec.c,v
retrieving revision 1.1.1.2
diff -u -r1.1.1.2 exec.c
--- exec.c 1999/01/23 16:28:07 1.1.1.2
+++ exec.c 1999/01/28 01:47:52
@@ -378,7 +378,7 @@
struct mm_struct * mm, * old_mm;
int retval, nr;
- if (atomic_read(¤t->mm->count) == 1) {
+ if (current->mm->count == 1) {
flush_cache_mm(current->mm);
mm_release();
release_segments(current->mm);
Index: fs/proc/array.c
===================================================================
RCS file: /var/cvs/linux/fs/proc/array.c,v
retrieving revision 1.1.1.4
diff -u -r1.1.1.4 array.c
--- array.c 1999/01/26 18:30:44 1.1.1.4
+++ array.c 1999/01/28 02:32:48
@@ -388,31 +388,6 @@
return sprintf(buffer, "%s\n", saved_command_line);
}
-/*
- * Caller must release_mm the mm_struct later.
- * You don't get any access to init_mm.
- */
-static struct mm_struct *get_mm_and_lock(int pid)
-{
- struct mm_struct *mm = NULL;
- struct task_struct *tsk;
-
- read_lock(&tasklist_lock);
- tsk = find_task_by_pid(pid);
- if (tsk && tsk->mm && tsk->mm != &init_mm)
- mmget(mm = tsk->mm);
- read_unlock(&tasklist_lock);
- if (mm != NULL)
- down(&mm->mmap_sem);
- return mm;
-}
-
-static void release_mm(struct mm_struct *mm)
-{
- up(&mm->mmap_sem);
- mmput(mm);
-}
-
static unsigned long get_phys_addr(struct mm_struct *mm, unsigned long ptr)
{
pgd_t *page_dir;
@@ -480,27 +455,35 @@
static int get_env(int pid, char * buffer)
{
- struct mm_struct *mm;
+ struct task_struct * tsk;
int res = 0;
- mm = get_mm_and_lock(pid);
- if (mm) {
+ read_lock(&tasklist_lock);
+ tsk = find_task_by_pid(pid);
+ if (tsk)
+ {
+ struct mm_struct * mm = tsk->mm;
res = get_array(mm, mm->env_start, mm->env_end, buffer);
- release_mm(mm);
}
+ read_unlock(&tasklist_lock);
+
return res;
}
static int get_arg(int pid, char * buffer)
{
- struct mm_struct *mm;
+ struct task_struct * tsk;
int res = 0;
- mm = get_mm_and_lock(pid);
- if (mm) {
+ read_lock(&tasklist_lock);
+ tsk = find_task_by_pid(pid);
+ if (tsk)
+ {
+ struct mm_struct * mm = tsk->mm;
res = get_array(mm, mm->arg_start, mm->arg_end, buffer);
- release_mm(mm);
}
+ read_unlock(&tasklist_lock);
+
return res;
}
@@ -849,39 +832,22 @@
cap_t(p->cap_effective));
}
-static struct task_struct *grab_task(int pid)
-{
- struct task_struct *tsk = current;
- if (pid != tsk->pid) {
- read_lock(&tasklist_lock);
- tsk = find_task_by_pid(pid);
- if (tsk && tsk->mm && tsk->mm != &init_mm)
- mmget(tsk->mm);
- read_unlock(&tasklist_lock);
- }
- return tsk;
-}
-
-static void release_task(struct task_struct *tsk)
-{
- if (tsk != current && tsk->mm && tsk->mm != &init_mm)
- mmput(tsk->mm);
-}
-
static int get_status(int pid, char * buffer)
{
char * orig = buffer;
- struct task_struct *tsk;
+ struct task_struct * tsk;
- tsk = grab_task(pid);
+ read_lock(&tasklist_lock);
+ tsk = find_task_by_pid(pid);
if (!tsk)
- return 0;
+ goto unlock;
buffer = task_name(tsk, buffer);
buffer = task_state(tsk, buffer);
buffer = task_mem(tsk, buffer);
buffer = task_sig(tsk, buffer);
buffer = task_cap(tsk, buffer);
- release_task(tsk);
+ unlock:
+ read_unlock(&tasklist_lock);
return buffer - orig;
}
@@ -893,21 +859,20 @@
int tty_pgrp;
sigset_t sigign, sigcatch;
char state;
- int res;
+ int res = 0;
- tsk = grab_task(pid);
+ read_lock(&tasklist_lock);
+ tsk = find_task_by_pid(pid);
if (!tsk)
- return 0;
+ goto unlock;
state = *get_task_state(tsk);
vsize = eip = esp = 0;
if (tsk->mm && tsk->mm != &init_mm) {
struct vm_area_struct *vma;
- down(&tsk->mm->mmap_sem);
for (vma = tsk->mm->mmap; vma; vma = vma->vm_next) {
vsize += vma->vm_end - vma->vm_start;
}
- up(&tsk->mm->mmap_sem);
eip = KSTK_EIP(tsk);
esp = KSTK_ESP(tsk);
@@ -975,7 +940,8 @@
tsk->cnswap,
tsk->exit_signal);
- release_task(tsk);
+ unlock:
+ read_unlock(&tasklist_lock);
return res;
}
@@ -1054,11 +1020,14 @@
static int get_statm(int pid, char * buffer)
{
+ struct task_struct * tsk;
int size=0, resident=0, share=0, trs=0, lrs=0, drs=0, dt=0;
- struct mm_struct *mm;
- mm = get_mm_and_lock(pid);
- if (mm) {
+ read_lock(&tasklist_lock);
+ tsk = find_task_by_pid(pid);
+ if (tsk)
+ {
+ struct mm_struct * mm = tsk->mm;
struct vm_area_struct * vma = mm->mmap;
while (vma) {
@@ -1080,8 +1049,8 @@
drs += pages;
vma = vma->vm_next;
}
- release_mm(mm);
}
+ read_unlock(&tasklist_lock);
return sprintf(buffer,"%d %d %d %d %d %d %d\n",
size, resident, share, trs, lrs, drs, dt);
}
@@ -1149,7 +1118,7 @@
goto getlen_out;
/* Check whether the mmaps could change if we sleep */
- volatile_task = (p != current || atomic_read(&p->mm->count) > 1);
+ volatile_task = (p != current || p->mm->count > 1);
/* decode f_pos */
lineno = *ppos >> MAPS_LINE_SHIFT;
@@ -1251,11 +1220,12 @@
static int get_pidcpu(int pid, char * buffer)
{
struct task_struct * tsk;
- int i, len;
+ int i, len = 0;
- tsk = grab_task(pid);
+ read_lock(&tasklist_lock);
+ tsk = find_task_by_pid(pid);
if (!tsk)
- return 0;
+ goto unlock;
len = sprintf(buffer,
"cpu %lu %lu\n",
@@ -1267,8 +1237,9 @@
i,
tsk->per_cpu_utime[cpu_logical_map(i)],
tsk->per_cpu_stime[cpu_logical_map(i)]);
+ unlock:
+ read_unlock(&tasklist_lock);
- release_task(tsk);
return len;
}
#endif
Index: include/asm-i386/pgtable.h
===================================================================
RCS file: /var/cvs/linux/include/asm-i386/pgtable.h,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 pgtable.h
--- pgtable.h 1999/01/18 01:27:15 1.1.1.1
+++ pgtable.h 1999/01/27 20:09:21
@@ -101,7 +101,7 @@
static inline void flush_tlb_current_task(void)
{
/* just one copy of this mm? */
- if (atomic_read(¤t->mm->count) == 1)
+ if (current->mm->count == 1)
local_flush_tlb(); /* and that's us, so.. */
else
smp_flush_tlb();
@@ -113,7 +113,7 @@
static inline void flush_tlb_mm(struct mm_struct * mm)
{
- if (mm == current->mm && atomic_read(&mm->count) == 1)
+ if (mm == current->mm && mm->count == 1)
local_flush_tlb();
else
smp_flush_tlb();
@@ -122,7 +122,7 @@
static inline void flush_tlb_page(struct vm_area_struct * vma,
unsigned long va)
{
- if (vma->vm_mm == current->mm && atomic_read(¤t->mm->count) == 1)
+ if (vma->vm_mm == current->mm && current->mm->count == 1)
__flush_tlb_one(va);
else
smp_flush_tlb();
Index: include/linux/sched.h
===================================================================
RCS file: /var/cvs/linux/include/linux/sched.h,v
retrieving revision 1.1.1.3
diff -u -r1.1.1.3 sched.h
--- sched.h 1999/01/23 16:29:58 1.1.1.3
+++ sched.h 1999/01/28 02:33:01
@@ -164,7 +164,7 @@
struct vm_area_struct *mmap_avl; /* tree of VMAs */
struct vm_area_struct *mmap_cache; /* last find_vma result */
pgd_t * pgd;
- atomic_t count;
+ int count;
int map_count; /* number of VMAs */
struct semaphore mmap_sem;
unsigned long context;
@@ -184,7 +184,7 @@
#define INIT_MM { \
&init_mmap, NULL, NULL, \
swapper_pg_dir, \
- ATOMIC_INIT(1), 1, \
+ 1, 1, \
MUTEX, \
0, \
0, 0, 0, 0, \
@@ -609,11 +609,11 @@
* Routines for handling mm_structs
*/
extern struct mm_struct * mm_alloc(void);
-static inline void mmget(struct mm_struct * mm)
+extern inline void mmget(struct mm_struct * mm)
{
- atomic_inc(&mm->count);
+ mm->count++;
}
-extern void mmput(struct mm_struct *);
+extern void FASTCALL(mmput(struct mm_struct *));
/* Remove the current tasks stale references to the old mm_struct */
extern void mm_release(void);
Index: kernel/fork.c
===================================================================
RCS file: /var/cvs/linux/kernel/fork.c,v
retrieving revision 1.1.1.3
diff -u -r1.1.1.3 fork.c
--- fork.c 1999/01/23 16:30:27 1.1.1.3
+++ fork.c 1999/01/28 01:52:53
@@ -261,7 +261,7 @@
if (mm) {
*mm = *current->mm;
init_new_context(mm);
- atomic_set(&mm->count, 1);
+ mm->count = 1;
mm->map_count = 0;
mm->def_flags = 0;
mm->mmap_sem = MUTEX_LOCKED;
@@ -308,7 +308,7 @@
*/
void mmput(struct mm_struct *mm)
{
- if (atomic_dec_and_test(&mm->count)) {
+ if (!--mm->count) {
release_segments(mm);
exit_mmap(mm);
free_page_tables(mm);
If you see a race in this my new patch, please let me know and probably
you'll give me a good reason to reinsert mm_lock ;)
Andrea Arcangeli
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