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Date: Thu, 11 Aug 2011 20:05:25 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Tim Sander <tim.sander@....com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
"Paul E. McKenney" <paulmck@...ibm.com>,
linux-rt-users <linux-rt-users@...r.kernel.org>,
John Stultz <johnstul@...ibm.com>
Subject: Re: [ANNOUNCE] 3.0.1-rt8 - Regression to 3.0-rt7
On Thu, 2011-08-11 at 18:14 +0200, Peter Zijlstra wrote:
> On Thu, 2011-08-11 at 18:04 +0200, Tim Sander wrote:
> >
> > kernel BUG at kernel/posix-cpu-timers.c:1315!
> > Unable to handle kernel NULL pointer dereference at virtual address 00000000
> > pgd = c0004000
> > [00000000] *pgd=00000000
> > Internal error: Oops: 817 [#1] PREEMPT
> > Modules linked in: i2c_imx(+) netx netx_reset dspload fpgaload mxc_nand(+) nand nand_ids nand_ecc
> > CPU: 0 Not tainted (3.0.0-pmx-rt8-00009-g39305ab #167)
> > PC is at __bug+0x24/0x30
> > LR is at walk_stackframe+0x24/0x40
> > pc : [<c002cbf0>] lr : [<c002cbb0>] psr: 60000113
> > sp : c782ff40 ip : c782fe28 fp : c782ff4c
> > r10: 00000001 r9 : 00000000 r8 : c78663c0
> > r7 : c030463c r6 : c782e000 r5 : 00000000 r4 : c78663c0
> > r3 : 00000000 r2 : 00000001 r1 : c782fe58 r0 : 00000034
> > Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
> > Control: 00c5387d Table: 87b70008 DAC: 00000017
> > Process posixcputmr/0 (pid: 6, stack limit = 0xc782e268)
> > Stack: (0xc782ff40 to 0xc7830000)
> > ff40: c782ff8c c782ff50 c005a5c0 c002cbd8 00000000 c782ff54 c782ff54 00000000
> > ff60: 00000000 c78663c0 00000000 c782e000 c030463c c78663c0 00000000 00000001
> > ff80: c782ffbc c782ff90 c005a88c c005a594 00000000 c7817f28 00000000 c782ffcc
> > ffa0: c005a800 00000000 00000000 00000000 c782fff4 c782ffc0 c00570f0 c005a80c
> > ffc0: c7817f28 00000000 00000000 00000000 c782ffd0 c782ffd0 c7817f28 c0057064
> > ffe0: c0040868 00000013 00000000 c782fff8 c0040868 c0057070 cccdcd6c ffdec890
> > Backtrace:
> > [<c002cbcc>] (__bug+0x0/0x30) from [<c005a5c0>] (__run_posix_cpu_timers+0x38/0x278)
> > [<c005a588>] (__run_posix_cpu_timers+0x0/0x278) from [<c005a88c>] (posix_cpu_timers_thread+0x8c/0x124)
> > [<c005a800>] (posix_cpu_timers_thread+0x0/0x124) from [<c00570f0>] (kthread+0x8c/0x94)
> > [<c0057064>] (kthread+0x0/0x94) from [<c0040868>] (do_exit+0x0/0x2d8)
> > r7:00000013 r6:c0040868 r5:c0057064 r4:c7817f28
> > Code: e59f0010 e1a01003 eb086a88 e3a03000 (e5833000)
> > ---[ end trace d632afeaa11559d4 ]---
>
> Yay a new one, and this is a PREEMPT_LL build right? /me goes poke at
> it.
---
Subject: posix-cpu-timer: Fixup PREEMPT_LL build
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Thu Aug 11 19:18:23 CEST 2011
Cc: john stultz <johnstul@...ibm.com>
Reported-by: Tim Sander <tim.sander@....com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
include/linux/init_task.h | 8 +++++++-
include/linux/sched.h | 2 ++
kernel/fork.c | 2 ++
kernel/posix-cpu-timers.c | 24 ++++++++++++++++--------
4 files changed, 27 insertions(+), 9 deletions(-)
Index: linux-2.6/include/linux/init_task.h
===================================================================
--- linux-2.6.orig/include/linux/init_task.h
+++ linux-2.6/include/linux/init_task.h
@@ -126,6 +126,12 @@ extern struct cred init_cred;
# define INIT_PERF_EVENTS(tsk)
#endif
+#ifdef CONFIG_PREEMPT_RT_BASE
+# define INIT_TIMER_LIST .posix_timer_list = NULL,
+#else
+# define INIT_TIMER_LIST
+#endif
+
/*
* INIT_TASK is used to set up the first task table, touch at
* your own risk!. Base=0, limit=0x1fffff (=2MB)
@@ -179,7 +185,7 @@ extern struct cred init_cred;
.fs_excl = ATOMIC_INIT(0), \
.pi_lock = __RAW_SPIN_LOCK_UNLOCKED(tsk.pi_lock), \
.timer_slack_ns = 50000, /* 50 usec default slack */ \
- .posix_timer_list = NULL, \
+ INIT_TIMER_LIST \
.pids = { \
[PIDTYPE_PID] = INIT_PID_LINK(PIDTYPE_PID), \
[PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID), \
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1364,7 +1364,9 @@ struct task_struct {
struct task_cputime cputime_expires;
struct list_head cpu_timers[3];
+#ifdef CONFIG_PREEMPT_RT_BASE
struct task_struct *posix_timer_list;
+#endif
/* process credentials */
const struct cred __rcu *real_cred; /* objective and real subjective task
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c
+++ linux-2.6/kernel/fork.c
@@ -1054,7 +1054,9 @@ void mm_init_owner(struct mm_struct *mm,
*/
static void posix_cpu_timers_init(struct task_struct *tsk)
{
+#ifdef CONFIG_PREEMPT_RT_BASE
tsk->posix_timer_list = NULL;
+#endif
tsk->cputime_expires.prof_exp = cputime_zero;
tsk->cputime_expires.virt_exp = cputime_zero;
tsk->cputime_expires.sched_exp = 0;
Index: linux-2.6/kernel/posix-cpu-timers.c
===================================================================
--- linux-2.6.orig/kernel/posix-cpu-timers.c
+++ linux-2.6/kernel/posix-cpu-timers.c
@@ -1370,6 +1370,7 @@ static void __run_posix_cpu_timers(struc
}
}
+#ifdef CONFIG_PREEMPT_RT_BASE
#include <linux/kthread.h>
#include <linux/cpu.h>
DEFINE_PER_CPU(struct task_struct *, posix_timer_task);
@@ -1532,14 +1533,26 @@ static struct notifier_block __devinitda
static int __init posix_cpu_thread_init(void)
{
- void *cpu = (void *)(long)smp_processor_id();
+ void *hcpu = (void *)(long)smp_processor_id();
/* Start one for boot CPU. */
- posix_cpu_thread_call(&posix_cpu_thread_notifier, CPU_UP_PREPARE, cpu);
- posix_cpu_thread_call(&posix_cpu_thread_notifier, CPU_ONLINE, cpu);
+ unsigned long cpu;
+
+ /* init the per-cpu posix_timer_tasklets */
+ for_each_cpu_mask(cpu, cpu_possible_map)
+ per_cpu(posix_timer_tasklist, cpu) = NULL;
+
+ posix_cpu_thread_call(&posix_cpu_thread_notifier, CPU_UP_PREPARE, hcpu);
+ posix_cpu_thread_call(&posix_cpu_thread_notifier, CPU_ONLINE, hcpu);
register_cpu_notifier(&posix_cpu_thread_notifier);
return 0;
}
early_initcall(posix_cpu_thread_init);
+#else /* CONFIG_PREEMPT_RT_BASE */
+void run_posix_cpu_timers(struct task_struct *tsk)
+{
+ __run_posix_cpu_timers(tsk);
+}
+#endif /* CONFIG_PREEMPT_RT_BASE */
/*
* Set one of the process-wide special case CPU timers or RLIMIT_CPU.
@@ -1789,11 +1802,6 @@ static __init int init_posix_cpu_timers(
.timer_create = thread_cpu_timer_create,
};
struct timespec ts;
- unsigned long cpu;
-
- /* init the per-cpu posix_timer_tasklets */
- for_each_cpu_mask(cpu, cpu_possible_map)
- per_cpu(posix_timer_tasklist, cpu) = NULL;
posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
--
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