From: Ingo Molnar <mingo@elte.hu>
To: William Lee Irwin III <wli@holomorphy.com>,
Anton Blanchard <anton@samba.org>,
linux-kernel@vger.kernel.org,
viro@parcelfarce.linux.theplanet.co.uk
Subject: Re: /proc/sys/kernel/pid_max issues
Date: Sun, 12 Sep 2004 12:13:50 +0200 [thread overview]
Message-ID: <20040912101350.GA13164@elte.hu> (raw)
In-Reply-To: <20040912095805.GL2660@holomorphy.com>
[-- Attachment #1: Type: text/plain, Size: 557 bytes --]
* William Lee Irwin III <wli@holomorphy.com> wrote:
> If pid_max == BITS_PER_PAGE*n, none of
> &pidmap_array[pid_max/BITS_PER_PAGE] is usable, so if we must complete
> a full revolution around pidmap_array[] to discover a free pid
> slightly less than last_pid we will miss it. Hence:
yeah. Patch needs testing ...
> if (++map == map_limit)
> map = pidmap_array;
> + if (map > &pidmap_array[(pid_max-1)/BITS_PER_PAGE])
> + map = pidmap_array;
in fact we can now merge the max_limit and pid_max checks - see the
attached updated patch.
Ingo
[-- Attachment #2: pid-max-fix.patch --]
[-- Type: text/plain, Size: 1373 bytes --]
fix pid_max handling. Wrap around correctly.
Signed-off-by: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- linux/kernel/pid.c.orig
+++ linux/kernel/pid.c
@@ -53,8 +53,6 @@ typedef struct pidmap {
static pidmap_t pidmap_array[PIDMAP_ENTRIES] =
{ [ 0 ... PIDMAP_ENTRIES-1 ] = { ATOMIC_INIT(BITS_PER_PAGE), NULL } };
-static pidmap_t *map_limit = pidmap_array + PIDMAP_ENTRIES;
-
static spinlock_t pidmap_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
fastcall void free_pidmap(int pid)
@@ -73,7 +71,9 @@ fastcall void free_pidmap(int pid)
static inline pidmap_t *next_free_map(pidmap_t *map, int *max_steps)
{
while (--*max_steps) {
- if (++map == map_limit)
+ pidmap_t *map_limit = pidmap_array + (pid_max-1)/BITS_PER_PAGE;
+
+ if (++map > map_limit)
map = pidmap_array;
if (unlikely(!map->page)) {
unsigned long page = get_zeroed_page(GFP_KERNEL);
@@ -133,13 +133,12 @@ next_map:
*/
scan_more:
offset = find_next_zero_bit(map->page, BITS_PER_PAGE, offset);
- if (offset >= BITS_PER_PAGE)
+ pid = (map - pidmap_array) * BITS_PER_PAGE + offset;
+ if (offset >= BITS_PER_PAGE || pid >= pid_max)
goto next_map;
if (test_and_set_bit(offset, map->page))
goto scan_more;
-
/* we got the PID: */
- pid = (map - pidmap_array) * BITS_PER_PAGE + offset;
goto return_pid;
failure:
next prev parent reply other threads:[~2004-09-12 10:13 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-12 8:56 /proc/sys/kernel/pid_max issues Anton Blanchard
2004-09-12 9:36 ` William Lee Irwin III
2004-09-12 9:51 ` Ingo Molnar
2004-09-12 9:58 ` William Lee Irwin III
2004-09-12 10:10 ` William Lee Irwin III
2004-09-12 10:13 ` Ingo Molnar [this message]
2004-09-12 10:43 ` William Lee Irwin III
2004-09-12 10:45 ` William Lee Irwin III
2004-09-12 11:08 ` William Lee Irwin III
2004-09-12 11:20 ` Ingo Molnar
2004-09-12 17:13 ` William Lee Irwin III
2004-09-12 18:02 ` Chris Wedgwood
2004-09-12 23:06 ` William Lee Irwin III
2004-09-13 1:46 ` [pidhashing] rewrite alloc_pidmap() William Lee Irwin III
2004-09-12 9:39 ` /proc/sys/kernel/pid_max issues Ingo Molnar
2004-09-12 9:43 ` William Lee Irwin III
2004-09-12 12:18 ` Arjan van de Ven
2004-09-12 12:30 ` Anton Blanchard
2004-09-12 12:44 ` Arjan van de Ven
2004-09-12 13:34 ` Anton Blanchard
2004-09-12 13:41 ` Ingo Molnar
-- strict thread matches above, loose matches on Subject: below --
2004-09-13 3:20 Albert Cahalan
2004-09-13 7:42 ` William Lee Irwin III
2004-09-13 14:11 ` Albert Cahalan
2004-09-13 14:27 ` William Lee Irwin III
2004-09-13 14:51 ` Herbert Poetzl
2004-09-14 2:13 ` William Lee Irwin III
2004-09-23 13:13 ` Pavel Machek
2004-09-24 16:02 ` Martin Mares
2004-09-23 13:11 ` Pavel Machek
2004-09-13 7:57 ` Ingo Molnar
2004-09-13 13:54 ` Albert Cahalan
2004-09-13 14:24 ` William Lee Irwin III
2004-09-13 14:54 ` Albert Cahalan
2004-09-14 2:02 ` William Lee Irwin III
2004-09-14 15:32 ` Ingo Molnar
2004-09-18 18:32 ` Pavel Machek
2004-09-23 13:18 ` Pavel Machek
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