* NULL dereference OOPS on SysRq-w
@ 2008-04-27 6:36 Dan Noe
2008-04-28 6:57 ` Dave Young
0 siblings, 1 reply; 5+ messages in thread
From: Dan Noe @ 2008-04-27 6:36 UTC (permalink / raw)
To: Linux Kernel Mailing List
I've experienced the following on a build done today from Linus's
linux-2.6 tree. After a fresh boot I do "echo "w" >
/proc/sysrq_trigger" and I get the OOPS, every time. I looked at the
sched_debug code but I admit I was lost. Not sure why sched.c includes
sched_debug.c.
Cheers,
Dan
Via netconsole:
SysRq : Show Blocked State
task PC stack pid father
Sched Debug Version: v0.07, 2.6.25 #12
now at 275558.648467 msecs
.sysctl_sched_latency : 40.000000
.sysctl_sched_min_granularity : 8.000000
.sysctl_sched_wakeup_granularity : 20.000000
.sysctl_sched_child_runs_first : 0.000001
.sysctl_sched_features : 895
cpu#0, 2194.491 MHz
.nr_running : 3
.load : 3145728
.nr_switches : 13171
.nr_load_updates : 6476
.nr_uninterruptible : -94
.jiffies : 4294961186
.next_balance : 4294.961046
.curr->pid : 3078
.clock : 101239.537371
.idle_clock : 0.000000
.prev_clock_raw : 296931.974646
.clock_warps : 0
.clock_overflows : 12189
.clock_underflows : 4657
.clock_deep_idle_events : 4
.clock_max_delta : 499.306905
.cpu_load[0] : 0
.cpu_load[1] : 96
.cpu_load[2] : 14028
.cpu_load[3] : 62524
.cpu_load[4] : 91704
cfs_rq[0]:
.exec_clock : 400.314576
.MIN_vruntime : 17300.019734
.min_vruntime : 2099676.053218
.max_vruntime : 17300.019734
.spread : 0.000000
.spread0 : 0.000000
.nr_running : 1
.load : 1024
.bkl_count : 353
.nr_spread_over : 44
.shares : 1024
cfs_rq[0]:
.exec_clock : 1.281845
.MIN_vruntime : 0.000001
.min_vruntime : 2099676.053218
.max_vruntime : 0.000001
.spread : 0.000000
.spread0 : 0.000000
.nr_running : 0
.load : 0
.bkl_count : 353
.nr_spread_over : 2
.shares : 0
cfs_rq[0]:
.exec_clock : 13.306219
.MIN_vruntime : 0.000001
.min_vruntime : 2099676.053218
.max_vruntime : 0.000001
.spread : 0.000000
.spread0 : 0.000000
.nr_running : 0
.load : 0
.bkl_count : 353
.nr_spread_over : 3
.shares : 0
cfs_rq[0]:
.exec_clock : 0.380305
.MIN_vruntime : 0.000001
.min_vruntime : 2099676.053218
.max_vruntime : 0.000001
.spread : 0.000000
.spread0 : 0.000000
.nr_running : 0
.load : 0
.bkl_count : 353
.nr_spread_over : 1
.shares : 0
cfs_rq[0]:
.exec_clock : 6.341858
.MIN_vruntime : 0.000001
.min_vruntime : 2099676.053218
.max_vruntime : 0.000001
.spread : 0.000000
.spread0 : 0.000000
.nr_running : 0
.load : 0
.bkl_count : 353
.nr_spread_over : 1
.shares : 0
cfs_rq[0]:
.exec_clock : 6.341858
.MIN_vruntime : 0.000001
.min_vruntime : 2099676.053218
.max_vruntime : 0.000001
.spread : 0.000000
.spread0 : 0.000000
.nr_running : 0
.load : 0
.bkl_count : 353
.nr_spread_over : 16
.shares : 1024
cfs_rq[0]:
.exec_clock : 12850.277817
.MIN_vruntime : 69710.961030
.min_vruntime : 2099676.053218
.max_vruntime : 69751.539537
.spread : 40.578507
.spread0 : 0.000000
.nr_running : 3
.load : 5169 .bkl_count
: 353 .nr_spread_over : 2038 .shares
: 2048BUG: unable to handle kernel NULL pointer dereference at
0000000000000018IP: [<ffffffff802b9ab6>] seq_printf+0x2e/0xa7
PGD 7dd05067 PUD 7e0fb067 PMD 0 Oops: 0000 [1] PREEMPT SMP
DEBUG_PAGEALLOCCPU 0
Modules linked in: netconsole nfsd lockd nfs_acl auth_rpcgss sunrpc
exportfs ac battery ipv6 dm_snapshot dm_mirror dm_log dm_mod eeprom
coretemp loop parport_pc parport snd_hda_intel rtc iTCO_wdt
iTCO_vendor_support i2c_i801 i2c_core snd_pc
m snd_timer snd soundcore snd_page_alloc button intel_agp evdev ext3 jbd
mbcache sd_mod ata_generic ata_piix pata_acpi libata scsi_mod dock
ehci_hcd uhci_hcd ide_pci_generic piix ide_core r8169 usbcore thermal
processor fan
Pid: 3078, comm: zsh Not tainted 2.6.25 #12
RIP: 0010:[<ffffffff802b9ab6>] [<ffffffff802b9ab6>] seq_printf+0x2e/0xa7
RSP: 0018:ffff81007e387c68 EFLAGS: 00010092
RAX: ffffffff804eec79 RBX: 0000000000000000 RCX: ffffee71806668f8
RDX: ffff810001091f80 RSI: ffffffff804eec79 RDI: 0000000000000000
RBP: ffff81007e387d48 R08: 0000000000000002 R09: ffffffff8024fb76
R10: 00000000d59bb5d6 R11: ffff81007e387968 R12: 0000000000000000
R13: 0000000000000000 R14: ffff810001091740 R15: 0000000000000007
FS: 00007f7dce0896e0(0000) GS:ffffffff8057a000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000018 CR3: 000000007e3ed000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process zsh (pid: 3078, threadinfo ffff81007e386000, task ffff81007e090000)
Stack: 0000000000000002 ffffffff8024fb76 ffff81007e090090 ffff81007e090000
ffffffff8022dc31 0000000000000046 ffff810001091f80 ffffee71806668f8
0000000000000002 ffffffff8024fb76 0000000000000096 0000000000000000
Call Trace:
[<ffffffff8024fb76>] ? up+0xf/0x39
[<ffffffff8022dc31>] ? print_cfs_rq+0x130/0x465
[<ffffffff8024fb76>] ? up+0xf/0x39
[<ffffffff8041dfa5>] ? _spin_unlock_irqrestore+0x66/0x74
[<ffffffff8022df57>] ? print_cfs_rq+0x456/0x465
[<ffffffff8022e920>] sched_debug_show+0x9ba/0xd28
[<ffffffff8022f978>] ? cpu_clock+0xf0/0xff
[<ffffffff802745fe>] ? get_timestamp+0x9/0xf
[<ffffffff80274628>] ? touch_softlockup_watchdog+0x24/0x2d
[<ffffffff802319ec>] show_state_filter+0x8b/0xaa
[<ffffffff80375848>] sysrq_handle_showstate_blocked+0xe/0x10
[<ffffffff803757a3>] __handle_sysrq+0x9e/0x135
[<ffffffff802e2544>] ? write_sysrq_trigger+0x0/0x3a
[<ffffffff802e2574>] write_sysrq_trigger+0x30/0x3a
[<ffffffff802dc6b2>] proc_reg_write+0x8a/0xa7
[<ffffffff802a0118>] vfs_write+0xa7/0xe1
[<ffffffff802a020c>] sys_write+0x47/0x6d
[<ffffffff8020c3ab>] system_call_after_swapgs+0x7b/0x80
Code: f0 48 89 e5 53 48 89 fb 48 81 ec d8 00 00 00 48 89 95 50 ff ff ff
48 89 8d 58 ff ff ff 4c 89 85 60 ff ff ff 4c 89 8d 68 ff ff ff <48> 8b
7f 18 48 3b 7b 08 73 5a 48 8b 73 08 48 8d 55 10 48 8d 8d
RIP [<ffffffff802b9ab6>] seq_printf+0x2e/0xa7
RSP <ffff81007e387c68>
CR2: 0000000000000018
---[ end trace ffd04a8c8a72749a ]---
note: zsh[3078] exited with preempt_count 2
BUG: sleeping function called from invalid context at kernel/rwsem.c:21
in_atomic():1, irqs_disabled():1
INFO: lockdep is turned off.
irq event stamp: 136430
hardirqs last enabled at (136429): [<ffffffff8041d4c0>]
trace_hardirqs_on_thunk+0x35/0x3a
hardirqs last disabled at (136430): [<ffffffff8041de72>]
_spin_lock_irqsave+0x19/0x73
softirqs last enabled at (131948): [<ffffffff8023dcec>]
__do_softirq+0x9e/0xa7
softirqs last disabled at (131911): [<ffffffff8020d68c>]
call_softirq+0x1c/0x28
Pid: 3078, comm: zsh Tainted: G D 2.6.25 #12
Call Trace:
[<ffffffff80255f3d>] ? print_irqtrace_events+0x110/0x114
[<ffffffff8022f7fc>] __might_sleep+0xda/0xdc
[<ffffffff8041c7f6>] down_read+0x20/0x68
[<ffffffff802681eb>] acct_collect+0x42/0x1a7
[<ffffffff8023ba57>] do_exit+0x205/0x713
[<ffffffff803723e2>] ? do_unblank_screen+0x29/0x125
[<ffffffff8020d90d>] oops_begin+0x0/0x8f
[<ffffffff80223c64>] do_page_fault+0x69f/0x757
[<ffffffff8041e2ed>] error_exit+0x0/0xa9
[<ffffffff8024fb76>] ? up+0xf/0x39
[<ffffffff802b9ab6>] ? seq_printf+0x2e/0xa7
[<ffffffff8024fb76>] ? up+0xf/0x39
[<ffffffff8022dc31>] ? print_cfs_rq+0x130/0x465
[<ffffffff8024fb76>] ? up+0xf/0x39
[<ffffffff8041dfa5>] ? _spin_unlock_irqrestore+0x66/0x74
[<ffffffff8022df57>] ? print_cfs_rq+0x456/0x465
[<ffffffff8022e920>] ? sched_debug_show+0x9ba/0xd28
[<ffffffff8022f978>] ? cpu_clock+0xf0/0xff
[<ffffffff802745fe>] ? get_timestamp+0x9/0xf
[<ffffffff80274628>] ? touch_softlockup_watchdog+0x24/0x2d
[<ffffffff802319ec>] ? show_state_filter+0x8b/0xaa
[<ffffffff80375848>] ? sysrq_handle_showstate_blocked+0xe/0x10
[<ffffffff803757a3>] ? __handle_sysrq+0x9e/0x135
[<ffffffff802e2544>] ? write_sysrq_trigger+0x0/0x3a
[<ffffffff802e2574>] ? write_sysrq_trigger+0x30/0x3a
[<ffffffff802dc6b2>] ? proc_reg_write+0x8a/0xa7
[<ffffffff802a0118>] ? vfs_write+0xa7/0xe1
[<ffffffff802a020c>] ? sys_write+0x47/0x6d
[<ffffffff8020c3ab>] ? system_call_after_swapgs+0x7b/0x80
--
/--------------- - - - - - -
| Dan Noe
| http://isomerica.net/~dpn/
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: NULL dereference OOPS on SysRq-w
2008-04-27 6:36 NULL dereference OOPS on SysRq-w Dan Noe
@ 2008-04-28 6:57 ` Dave Young
2008-04-28 7:01 ` Dan Noe
0 siblings, 1 reply; 5+ messages in thread
From: Dave Young @ 2008-04-28 6:57 UTC (permalink / raw)
To: Dan Noe; +Cc: Linux Kernel Mailing List, mingo
On Sun, Apr 27, 2008 at 02:36:42AM -0400, Dan Noe wrote:
> I've experienced the following on a build done today from Linus's linux-2.6
> tree. After a fresh boot I do "echo "w" > /proc/sysrq_trigger" and I get
> the OOPS, every time. I looked at the sched_debug code but I admit I was
> lost. Not sure why sched.c includes sched_debug.c.
>
> Cheers,
> Dan
>
> Via netconsole:
>
> SysRq : Show Blocked State
> task PC stack pid father
> Sched Debug Version: v0.07, 2.6.25 #12
> now at 275558.648467 msecs
[snip]
> : 2038 .shares : 2048BUG: unable to handle kernel
> NULL pointer dereference at 0000000000000018IP: [<ffffffff802b9ab6>]
> seq_printf+0x2e/0xa7
> PGD 7dd05067 PUD 7e0fb067 PMD 0 Oops: 0000 [1] PREEMPT SMP
> DEBUG_PAGEALLOCCPU 0
> Modules linked in: netconsole nfsd lockd nfs_acl auth_rpcgss sunrpc
> exportfs ac battery ipv6 dm_snapshot dm_mirror dm_log dm_mod eeprom
> coretemp loop parport_pc parport snd_hda_intel rtc iTCO_wdt
> iTCO_vendor_support i2c_i801 i2c_core snd_pc
> m snd_timer snd soundcore snd_page_alloc button intel_agp evdev ext3 jbd
> mbcache sd_mod ata_generic ata_piix pata_acpi libata scsi_mod dock ehci_hcd
> uhci_hcd ide_pci_generic piix ide_core r8169 usbcore thermal processor fan
> Pid: 3078, comm: zsh Not tainted 2.6.25 #12
> RIP: 0010:[<ffffffff802b9ab6>] [<ffffffff802b9ab6>] seq_printf+0x2e/0xa7
> RSP: 0018:ffff81007e387c68 EFLAGS: 00010092
> RAX: ffffffff804eec79 RBX: 0000000000000000 RCX: ffffee71806668f8
> RDX: ffff810001091f80 RSI: ffffffff804eec79 RDI: 0000000000000000
> RBP: ffff81007e387d48 R08: 0000000000000002 R09: ffffffff8024fb76
> R10: 00000000d59bb5d6 R11: ffff81007e387968 R12: 0000000000000000
> R13: 0000000000000000 R14: ffff810001091740 R15: 0000000000000007
> FS: 00007f7dce0896e0(0000) GS:ffffffff8057a000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 0000000000000018 CR3: 000000007e3ed000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process zsh (pid: 3078, threadinfo ffff81007e386000, task ffff81007e090000)
> Stack: 0000000000000002 ffffffff8024fb76 ffff81007e090090 ffff81007e090000
> ffffffff8022dc31 0000000000000046 ffff810001091f80 ffffee71806668f8
> 0000000000000002 ffffffff8024fb76 0000000000000096 0000000000000000
> Call Trace:
> [<ffffffff8024fb76>] ? up+0xf/0x39
> [<ffffffff8022dc31>] ? print_cfs_rq+0x130/0x465
> [<ffffffff8024fb76>] ? up+0xf/0x39
> [<ffffffff8041dfa5>] ? _spin_unlock_irqrestore+0x66/0x74
> [<ffffffff8022df57>] ? print_cfs_rq+0x456/0x465
> [<ffffffff8022e920>] sched_debug_show+0x9ba/0xd28
> [<ffffffff8022f978>] ? cpu_clock+0xf0/0xff
> [<ffffffff802745fe>] ? get_timestamp+0x9/0xf
> [<ffffffff80274628>] ? touch_softlockup_watchdog+0x24/0x2d
> [<ffffffff802319ec>] show_state_filter+0x8b/0xaa
> [<ffffffff80375848>] sysrq_handle_showstate_blocked+0xe/0x10
> [<ffffffff803757a3>] __handle_sysrq+0x9e/0x135
> [<ffffffff802e2544>] ? write_sysrq_trigger+0x0/0x3a
> [<ffffffff802e2574>] write_sysrq_trigger+0x30/0x3a
> [<ffffffff802dc6b2>] proc_reg_write+0x8a/0xa7
> [<ffffffff802a0118>] vfs_write+0xa7/0xe1
> [<ffffffff802a020c>] sys_write+0x47/0x6d
> [<ffffffff8020c3ab>] system_call_after_swapgs+0x7b/0x80
> Code: f0 48 89 e5 53 48 89 fb 48 81 ec d8 00 00 00 48 89 95 50 ff ff ff 48
> 89 8d 58 ff ff ff 4c 89 85 60 ff ff ff 4c 89 8d 68 ff ff ff <48> 8b 7f 18
> 48 3b 7b 08 73 5a 48 8b 73 08 48 8d 55 10 48 8d 8d
> RIP [<ffffffff802b9ab6>] seq_printf+0x2e/0xa7
> RSP <ffff81007e387c68>
> CR2: 0000000000000018
> ---[ end trace ffd04a8c8a72749a ]---
[snip]
I have a fix for the NULL pointer reference BUG, tested on my pc.
---
"m" will be NULL if seq_printf & seq_puts is called from sched_debug_show
Use SEQ_* macros to fix it
Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
---
include/linux/sched.h | 22 ++++++++++++++++++++++
kernel/sched_debug.c | 12 ------------
kernel/sched_fair.c | 6 +++---
3 files changed, 25 insertions(+), 15 deletions(-)
diff -upr linux/include/linux/sched.h linux.new/include/linux/sched.h
--- linux/include/linux/sched.h 2008-04-28 14:27:25.000000000 +0800
+++ linux.new/include/linux/sched.h 2008-04-28 14:37:45.000000000 +0800
@@ -2145,6 +2145,28 @@ static inline void migration_init(void)
#define TASK_SIZE_OF(tsk) TASK_SIZE
#endif
+#ifdef CONFIG_SCHED_DEBUG
+/*
+ * This allows printing both to /proc/sched_debug and
+ * to the console
+ */
+#define SEQ_printf(m, x...) \
+ do { \
+ if (m) \
+ seq_printf(m, x); \
+ else \
+ printk(x); \
+ } while (0)
+
+#define SEQ_puts(m, x...) \
+ do { \
+ if (m) \
+ seq_puts(m, x); \
+ else \
+ printk(x); \
+ } while (0)
+#endif
+
#endif /* __KERNEL__ */
#endif
diff -upr linux/kernel/sched_debug.c linux.new/kernel/sched_debug.c
--- linux/kernel/sched_debug.c 2008-04-28 14:24:02.000000000 +0800
+++ linux.new/kernel/sched_debug.c 2008-04-28 14:37:32.000000000 +0800
@@ -17,18 +17,6 @@
#include <linux/utsname.h>
/*
- * This allows printing both to /proc/sched_debug and
- * to the console
- */
-#define SEQ_printf(m, x...) \
- do { \
- if (m) \
- seq_printf(m, x); \
- else \
- printk(x); \
- } while (0)
-
-/*
* Ease the printing of nsec fields:
*/
static long long nsec_high(unsigned long long nsec)
diff -upr linux/kernel/sched_fair.c linux.new/kernel/sched_fair.c
--- linux/kernel/sched_fair.c 2008-04-28 14:16:17.000000000 +0800
+++ linux.new/kernel/sched_fair.c 2008-04-28 14:37:24.000000000 +0800
@@ -1623,9 +1623,9 @@ print_cfs_rq_tasks(struct seq_file *m, s
int i;
for (i = depth; i; i--)
- seq_puts(m, " ");
+ SEQ_puts(m, " ");
- seq_printf(m, "%lu %s %lu\n",
+ SEQ_printf(m, "%lu %s %lu\n",
se->load.weight,
entity_is_task(se) ? "T" : "G",
calc_delta_weight(SCHED_LOAD_SCALE, se)
@@ -1643,7 +1643,7 @@ static void print_cfs_stats(struct seq_f
for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
print_cfs_rq(m, cpu, cfs_rq);
- seq_printf(m, "\nWeight tree:\n");
+ SEQ_printf(m, "\nWeight tree:\n");
print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
rcu_read_unlock();
}
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: NULL dereference OOPS on SysRq-w
2008-04-28 6:57 ` Dave Young
@ 2008-04-28 7:01 ` Dan Noe
2008-04-28 7:08 ` Dave Young
0 siblings, 1 reply; 5+ messages in thread
From: Dan Noe @ 2008-04-28 7:01 UTC (permalink / raw)
To: Dave Young; +Cc: Linux Kernel Mailing List, mingo
Dave Young wrote:
> [snip]
>
> I have a fix for the NULL pointer reference BUG, tested on my pc.
> ---
>
> "m" will be NULL if seq_printf & seq_puts is called from sched_debug_show
> Use SEQ_* macros to fix it
>
> Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
There is actually already a patch out for this which simply hasn't made
it upstream yet - Mike Galbraith emailed me with it and it indeed fixes
the problem. I hadn't realized his email didn't go to lkml.. otherwise
I would have echoed that here to avoid wasting people's time. My apologies.
Cheers,
Dan
===
Here is his message:
From: efault@gmx.de
Peter's fix didn't make it up-stream.
Subject: sched: fix oops
sched_debug uses SEQ_printf to use printk when the seqfile 'm' is NULL.
Instead of doing that here too; choose to not output the weight tree
to cut back on output.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 89fa32b..353a481 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1643,8 +1643,10 @@ static void print_cfs_stats(struct seq_file *m,
int cpu)
for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
print_cfs_rq(m, cpu, cfs_rq);
- seq_printf(m, "\nWeight tree:\n");
- print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
+ if (m) {
+ seq_printf(m, "\nWeight tree:\n");
+ print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
+ }
rcu_read_unlock();
}
#endif
--
/--------------- - - - - - -
| Dan Noe
| http://isomerica.net/~dpn/
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: NULL dereference OOPS on SysRq-w
2008-04-28 7:01 ` Dan Noe
@ 2008-04-28 7:08 ` Dave Young
2008-04-28 7:26 ` Dave Young
0 siblings, 1 reply; 5+ messages in thread
From: Dave Young @ 2008-04-28 7:08 UTC (permalink / raw)
To: dpn; +Cc: Linux Kernel Mailing List, mingo
On Mon, Apr 28, 2008 at 3:01 PM, Dan Noe <dpn@isomerica.net> wrote:
> Dave Young wrote:
>
> > [snip]
> >
> > I have a fix for the NULL pointer reference BUG, tested on my pc.
> > ---
> >
> > "m" will be NULL if seq_printf & seq_puts is called from sched_debug_show
> > Use SEQ_* macros to fix it
> > Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
> >
>
> There is actually already a patch out for this which simply hasn't made it
> upstream yet - Mike Galbraith emailed me with it and it indeed fixes the
> problem. I hadn't realized his email didn't go to lkml.. otherwise I would
> have echoed that here to avoid wasting people's time. My apologies.
Ok, thanks.
While debuging this issue I found another BUG about sysrq,
echo w >/proc/sys/kernel/sysrq
My system hangs, there's no response from then on.
>
> Cheers,
> Dan
>
> ===
>
> Here is his message:
>
> From: efault@gmx.de
>
> Peter's fix didn't make it up-stream.
>
> Subject: sched: fix oops
>
> sched_debug uses SEQ_printf to use printk when the seqfile 'm' is NULL.
> Instead of doing that here too; choose to not output the weight tree
> to cut back on output.
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
> diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> index 89fa32b..353a481 100644
> --- a/kernel/sched_fair.c
> +++ b/kernel/sched_fair.c
> @@ -1643,8 +1643,10 @@ static void print_cfs_stats(struct seq_file *m, int
> cpu)
>
> for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
> print_cfs_rq(m, cpu, cfs_rq);
>
> - seq_printf(m, "\nWeight tree:\n");
> - print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
> + if (m) {
> + seq_printf(m, "\nWeight tree:\n");
>
> + print_cfs_rq_tasks(m, &cpu_rq(cpu)->cfs, 1);
> + }
> rcu_read_unlock();
> }
> #endif
>
>
>
>
> --
> /--------------- - - - - - -
> | Dan Noe
> | http://isomerica.net/~dpn/
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: NULL dereference OOPS on SysRq-w
2008-04-28 7:08 ` Dave Young
@ 2008-04-28 7:26 ` Dave Young
0 siblings, 0 replies; 5+ messages in thread
From: Dave Young @ 2008-04-28 7:26 UTC (permalink / raw)
To: dpn; +Cc: Linux Kernel Mailing List, mingo
On Mon, Apr 28, 2008 at 3:08 PM, Dave Young <hidave.darkstar@gmail.com> wrote:
> On Mon, Apr 28, 2008 at 3:01 PM, Dan Noe <dpn@isomerica.net> wrote:
> > Dave Young wrote:
> >
> > > [snip]
> > >
> > > I have a fix for the NULL pointer reference BUG, tested on my pc.
> > > ---
> > >
> > > "m" will be NULL if seq_printf & seq_puts is called from sched_debug_show
> > > Use SEQ_* macros to fix it
> > > Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
> > >
> >
> > There is actually already a patch out for this which simply hasn't made it
> > upstream yet - Mike Galbraith emailed me with it and it indeed fixes the
> > problem. I hadn't realized his email didn't go to lkml.. otherwise I would
> > have echoed that here to avoid wasting people's time. My apologies.
>
> Ok, thanks.
>
> While debuging this issue I found another BUG about sysrq,
>
> echo w >/proc/sys/kernel/sysrq
> My system hangs, there's no response from then on.
Strange, the bug can not be reproduced now. Now I only get the
expected result "Invalid argument".
^ permalink raw reply [flat|nested] 5+ messages in thread
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Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2008-04-27 6:36 NULL dereference OOPS on SysRq-w Dan Noe
2008-04-28 6:57 ` Dave Young
2008-04-28 7:01 ` Dan Noe
2008-04-28 7:08 ` Dave Young
2008-04-28 7:26 ` Dave Young
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