Re: current->sched_class->yield_task is NULL, any hint?

2014-04-19 Thread Lin Ming
On Sat, Apr 19, 2014 at 9:21 AM, Paul Gortmaker wrote: > On Wed, Apr 9, 2014 at 5:39 PM, Lin Ming wrote: >> On Wed, Apr 9, 2014 at 1:08 PM, Peter Zijlstra wrote: > > [...] > >>>> >>>> Look at that, its calling yield() from a non-preemptible context

Re: current-sched_class-yield_task is NULL, any hint?

2014-04-19 Thread Lin Ming
On Sat, Apr 19, 2014 at 9:21 AM, Paul Gortmaker paul.gortma...@windriver.com wrote: On Wed, Apr 9, 2014 at 5:39 PM, Lin Ming min...@gmail.com wrote: On Wed, Apr 9, 2014 at 1:08 PM, Peter Zijlstra pet...@infradead.org wrote: [...] Look at that, its calling yield() from a non-preemptible

Re: current->sched_class->yield_task is NULL, any hint?

2014-04-09 Thread Lin Ming
On Wed, Apr 9, 2014 at 1:08 PM, Peter Zijlstra wrote: > On Wed, Apr 09, 2014 at 09:47:42PM +0200, Peter Zijlstra wrote: >> On Wed, Apr 09, 2014 at 10:43:32AM -0700, Lin Ming wrote: >> > [12890.586996] [] (sys_sched_yield+0x0/0x90) from [] >> > (yield+0x2c/0x30) >&

Re: current->sched_class->yield_task is NULL, any hint?

2014-04-09 Thread Lin Ming
On Wed, Apr 9, 2014 at 11:32 AM, Lin Ming wrote: > On Wed, Apr 9, 2014 at 11:25 AM, Peter Zijlstra wrote: >> On Wed, Apr 09, 2014 at 10:43:32AM -0700, Lin Ming wrote: >>> Hi Peter, >>> >>> I hit a panic in sys_sched_yield() because(for some unknown reason)

Re: current->sched_class->yield_task is NULL, any hint?

2014-04-09 Thread Lin Ming
On Wed, Apr 9, 2014 at 11:25 AM, Peter Zijlstra wrote: > On Wed, Apr 09, 2014 at 10:43:32AM -0700, Lin Ming wrote: >> Hi Peter, >> >> I hit a panic in sys_sched_yield() because(for some unknown reason) >> current->sched_class->yield_task is NULL. >> It's a

current->sched_class->yield_task is NULL, any hint?

2014-04-09 Thread Lin Ming
Hi Peter, I hit a panic in sys_sched_yield() because(for some unknown reason) current->sched_class->yield_task is NULL. It's an ARM embedded board with 3.4-rt kernel. Could you share any hint for the possible causes? Panic log attached. Line 4551 "yield_task" is NULL. 4546

current-sched_class-yield_task is NULL, any hint?

2014-04-09 Thread Lin Ming
Hi Peter, I hit a panic in sys_sched_yield() because(for some unknown reason) current-sched_class-yield_task is NULL. It's an ARM embedded board with 3.4-rt kernel. Could you share any hint for the possible causes? Panic log attached. Line 4551 yield_task is NULL. 4546

Re: current-sched_class-yield_task is NULL, any hint?

2014-04-09 Thread Lin Ming
On Wed, Apr 9, 2014 at 11:25 AM, Peter Zijlstra pet...@infradead.org wrote: On Wed, Apr 09, 2014 at 10:43:32AM -0700, Lin Ming wrote: Hi Peter, I hit a panic in sys_sched_yield() because(for some unknown reason) current-sched_class-yield_task is NULL. It's an ARM embedded board with 3.4-rt

Re: current-sched_class-yield_task is NULL, any hint?

2014-04-09 Thread Lin Ming
On Wed, Apr 9, 2014 at 11:32 AM, Lin Ming min...@gmail.com wrote: On Wed, Apr 9, 2014 at 11:25 AM, Peter Zijlstra pet...@infradead.org wrote: On Wed, Apr 09, 2014 at 10:43:32AM -0700, Lin Ming wrote: Hi Peter, I hit a panic in sys_sched_yield() because(for some unknown reason) current

Re: current-sched_class-yield_task is NULL, any hint?

2014-04-09 Thread Lin Ming
On Wed, Apr 9, 2014 at 1:08 PM, Peter Zijlstra pet...@infradead.org wrote: On Wed, Apr 09, 2014 at 09:47:42PM +0200, Peter Zijlstra wrote: On Wed, Apr 09, 2014 at 10:43:32AM -0700, Lin Ming wrote: [12890.586996] [c007a364] (sys_sched_yield+0x0/0x90) from [c03cbf90] (yield+0x2c/0x30

Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data"

2013-09-25 Thread Lin Ming
On Wed, 2013-09-25 at 07:30 -0400, Peter Hurley wrote: > On 09/25/2013 05:04 AM, Lin Ming wrote: > > On Wed, Sep 18, 2013 at 8:22 AM, Peter Hurley > > wrote: > > [snip] > >> > >> Looking over vmalloc.c, the critical section footprint of the > >>

Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data"

2013-09-25 Thread Lin Ming
On Wed, Sep 25, 2013 at 7:30 PM, Peter Hurley wrote: > On 09/25/2013 05:04 AM, Lin Ming wrote: >> >> On Wed, Sep 18, 2013 at 8:22 AM, Peter Hurley >> wrote: >> [snip] >>> >>> >>> Looking over vmalloc.c, the critical section footprint of

Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data"

2013-09-25 Thread Lin Ming
but didn't find obvious way to reduce the critical section footprint. Could you share some hints how to do this? Thanks, Lin Ming > > Regards, > Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@v

Re: increased vmap_area_lock contentions on n_tty: Move buffers into n_tty_data

2013-09-25 Thread Lin Ming
vmallo.c, but didn't find obvious way to reduce the critical section footprint. Could you share some hints how to do this? Thanks, Lin Ming Regards, Peter Hurley -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More

Re: increased vmap_area_lock contentions on n_tty: Move buffers into n_tty_data

2013-09-25 Thread Lin Ming
On Wed, Sep 25, 2013 at 7:30 PM, Peter Hurley pe...@hurleysoftware.com wrote: On 09/25/2013 05:04 AM, Lin Ming wrote: On Wed, Sep 18, 2013 at 8:22 AM, Peter Hurley pe...@hurleysoftware.com wrote: [snip] Looking over vmalloc.c, the critical section footprint of the vmap_area_lock could

Re: increased vmap_area_lock contentions on n_tty: Move buffers into n_tty_data

2013-09-25 Thread Lin Ming
On Wed, 2013-09-25 at 07:30 -0400, Peter Hurley wrote: On 09/25/2013 05:04 AM, Lin Ming wrote: On Wed, Sep 18, 2013 at 8:22 AM, Peter Hurley pe...@hurleysoftware.com wrote: [snip] Looking over vmalloc.c, the critical section footprint of the vmap_area_lock could definitely

Re: [RFC PATCH] seqlock: add lockdep support

2013-09-18 Thread Lin Ming
On Wed, 2013-09-18 at 11:15 +0200, Peter Zijlstra wrote: > On Wed, Sep 18, 2013 at 02:57:13PM +0800, Lin Ming wrote: > > Hi, > > > > lockdep support for seqlock was discussed at: > > http://marc.info/?l=linux-kernel=137875860600648=2 > > > > This is

[RFC PATCH] seqlock: add lockdep support

2013-09-18 Thread Lin Ming
Hi, lockdep support for seqlock was discussed at: http://marc.info/?l=linux-kernel=137875860600648=2 This is very draft patch to add lockdep support for seqlock. Actually, it doesn't work yet. I throw it out to get comments and help. TODO: - fix seqlock usage in vdso code I got below with this

[RFC PATCH] seqlock: add lockdep support

2013-09-18 Thread Lin Ming
Hi, lockdep support for seqlock was discussed at: http://marc.info/?l=linux-kernelm=137875860600648w=2 This is very draft patch to add lockdep support for seqlock. Actually, it doesn't work yet. I throw it out to get comments and help. TODO: - fix seqlock usage in vdso code I got below with

Re: [RFC PATCH] seqlock: add lockdep support

2013-09-18 Thread Lin Ming
On Wed, 2013-09-18 at 11:15 +0200, Peter Zijlstra wrote: On Wed, Sep 18, 2013 at 02:57:13PM +0800, Lin Ming wrote: Hi, lockdep support for seqlock was discussed at: http://marc.info/?l=linux-kernelm=137875860600648w=2 This is very draft patch to add lockdep support for seqlock

Re: kernel deadlock

2013-09-10 Thread Lin Ming
On Wed, Sep 11, 2013 at 12:38 AM, John Stultz wrote: > On 09/10/2013 01:59 AM, Lin Ming wrote: >> On Tue, Sep 10, 2013 at 4:29 AM, John Stultz wrote: >> >> [snip] >> >>> So I think I've managed to finally reproduce this and hunt it down. >>> >>

Re: kernel deadlock

2013-09-10 Thread Lin Ming
_get_update_offsets(). > in ktime_get() and ktime_get_update_offsets(), which suggested a > seqcount deadlock (basically calling something that reads the seqlock > while we hold the write on it). HRTICK enabled, then I can reproduce this simply with, while [ 1 ] ; adjtimex -t 9999 done And your patch

Re: kernel deadlock

2013-09-10 Thread Lin Ming
() and ktime_get_update_offsets(), which suggested a seqcount deadlock (basically calling something that reads the seqlock while we hold the write on it). HRTICK enabled, then I can reproduce this simply with, while [ 1 ] ; adjtimex -t done And your patch fixed it. Thanks, Lin Ming

Re: kernel deadlock

2013-09-10 Thread Lin Ming
On Wed, Sep 11, 2013 at 12:38 AM, John Stultz john.stu...@linaro.org wrote: On 09/10/2013 01:59 AM, Lin Ming wrote: On Tue, Sep 10, 2013 at 4:29 AM, John Stultz john.stu...@linaro.org wrote: [snip] So I think I've managed to finally reproduce this and hunt it down. With Peter's sched: Fix

Re: soft lockup in sysvipc code.

2013-09-05 Thread Lin Ming
ode stuck at somewhere with preemption disabled. Look at the code, preemption disabled at: sysvipc_proc_next -> sysvipc_find_ipc -> ipc_lock_by_ptr enabled at: sysvipc_proc_next -> ipc_unlock or sysvipc_proc_stop -> ipc_unlock And I didn't find code may stuck in the path. I may miss s

Re: soft lockup in sysvipc code.

2013-09-05 Thread Lin Ming
at somewhere with preemption disabled. Look at the code, preemption disabled at: sysvipc_proc_next - sysvipc_find_ipc - ipc_lock_by_ptr enabled at: sysvipc_proc_next - ipc_unlock or sysvipc_proc_stop - ipc_unlock And I didn't find code may stuck in the path. I may miss something .. Regards, Lin Ming

Re: Unsigned widening casts of binary "not" operations..

2013-04-24 Thread Lin Ming
>> should also be double checked whether the high words are really not >> reserved and can be written to ...] > > Hi Ingo! Ufortunately I don't have access to real p4 hardware, > thus I'm CC'ing Ming who has been helping a lot in testing > this code pieces. Hi, Sorry, but I

Re: Unsigned widening casts of binary not operations..

2013-04-24 Thread Lin Ming
hardware, thus I'm CC'ing Ming who has been helping a lot in testing this code pieces. Hi, Sorry, but I don't have access to p4 hardware either. Lin Ming Still the patch itself is perfectly fine to me Reviewed-by: Cyrill Gorcunov gorcu...@openvz.org -- To unsubscribe from this list: send

Re: IPv6 deadlock with CONFIG_IPV6_ROUTER_PREF

2012-08-23 Thread Lin Ming
present everywhere. How about moving the garbage collection to a kernel thread? Then the write_lock(tb6_lock) in this kernel thread won't cause such kind of dead lock with other threads. Lin Ming > > Stack trace below. > > Thanks, > Debabrata > > [46476.055009] Pid: 7963, comm:

Re: IPv6 deadlock with CONFIG_IPV6_ROUTER_PREF

2012-08-23 Thread Lin Ming
everywhere. How about moving the garbage collection to a kernel thread? Then the write_lock(tb6_lock) in this kernel thread won't cause such kind of dead lock with other threads. Lin Ming Stack trace below. Thanks, Debabrata [46476.055009] Pid: 7963, comm: Not tainted 2.6.38-amd64

Re: IPv4 BUG: held lock freed!

2012-08-19 Thread Lin Ming
On Sun, Aug 19, 2012 at 10:45 PM, Eric Dumazet wrote: > On Sun, 2012-08-19 at 22:15 +0800, Lin Ming wrote: > >> Will it still has problem if code goes here without sock_hold(sk)? > > Not sure of what you mean. See my comments in the function. Is that a potential pro

Re: IPv4 BUG: held lock freed!

2012-08-19 Thread Lin Ming
On Sun, Aug 19, 2012 at 8:51 PM, Eric Dumazet wrote: > Hi Fengguang, thanks for this report. > > Hmm, this looks like sk_reset_timer() is called on a socket, and timer > triggers _before_ the sock_hold() > > So the timer handler decrements sk_refcnt to 0 and calls sk_free() > > Its probably a

Re: IPv4 BUG: held lock freed!

2012-08-19 Thread Lin Ming
On Sun, Aug 19, 2012 at 8:51 PM, Eric Dumazet eric.duma...@gmail.com wrote: snip... Hi Fengguang, thanks for this report. Hmm, this looks like sk_reset_timer() is called on a socket, and timer triggers _before_ the sock_hold() So the timer handler decrements sk_refcnt to 0 and calls

Re: IPv4 BUG: held lock freed!

2012-08-19 Thread Lin Ming
On Sun, Aug 19, 2012 at 10:45 PM, Eric Dumazet eric.duma...@gmail.com wrote: On Sun, 2012-08-19 at 22:15 +0800, Lin Ming wrote: Will it still has problem if code goes here without sock_hold(sk)? Not sure of what you mean. See my comments in the function. Is that a potential problem? static