Re: possible recursive locking, 2.6.24-rc7
Denys Fedoryshchenko wrote: > I cannot reproduce, it is happened with rtorrent just randomly. But i will > patch and keep watching. > > On Sun, 13 Jan 2008 19:44:26 +0100, Peter Zijlstra wrote >> On Sun, 2008-01-13 at 17:22 +0100, Peter Zijlstra wrote: >> > It's epoll, this is a known issue and will be fixed soon. Thanks for >> > reporting. >> >> If its easy for you to reproduce, would you mind giving the following >> patch a spin? I may have a way to trigger another epoll "recursive-locking" trace at will with current firewire development code. Will try the annotation patch when I have time. https://bugzilla.redhat.com/show_bug.cgi?id=323411 http://marc.info/?l=linux1394-devel=120006699425902 -- Stefan Richter -=-==--- ---= -===- http://arcgraph.de/sr/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: possible recursive locking, 2.6.24-rc7
Denys Fedoryshchenko wrote: I cannot reproduce, it is happened with rtorrent just randomly. But i will patch and keep watching. On Sun, 13 Jan 2008 19:44:26 +0100, Peter Zijlstra wrote On Sun, 2008-01-13 at 17:22 +0100, Peter Zijlstra wrote: It's epoll, this is a known issue and will be fixed soon. Thanks for reporting. If its easy for you to reproduce, would you mind giving the following patch a spin? I may have a way to trigger another epoll recursive-locking trace at will with current firewire development code. Will try the annotation patch when I have time. https://bugzilla.redhat.com/show_bug.cgi?id=323411 http://marc.info/?l=linux1394-develm=120006699425902 -- Stefan Richter -=-==--- ---= -===- http://arcgraph.de/sr/ -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: possible recursive locking, 2.6.24-rc7
I cannot reproduce, it is happened with rtorrent just randomly. But i will
patch and keep watching.
On Sun, 13 Jan 2008 19:44:26 +0100, Peter Zijlstra wrote
> On Sun, 2008-01-13 at 17:22 +0100, Peter Zijlstra wrote:
> > On Sun, 2008-01-13 at 17:51 +0200, Denys Fedoryshchenko wrote:
> > > Hi, got in dmesg
> > > Not sure where to send (there is TCP), so sending netdev@ and kernel@
> >
> > It's epoll, this is a known issue and will be fixed soon. Thanks for
> > reporting.
>
> If its easy for you to reproduce, would you mind giving the following
> patch a spin?
>
> ---
>
> Subject: lockdep: annotate epoll
>
> On Sat, 2008-01-05 at 13:35 -0800, Davide Libenzi wrote:
>
> > I remember I talked with Arjan about this time ago. Basically, since 1)
> > you can drop an epoll fd inside another epoll fd 2) callback-based wakeups
> > are used, you can see a wake_up() from inside another wake_up(), but they
> > will never refer to the same lock instance.
> > Think about:
> >
> > dfd = socket(...);
> > efd1 = epoll_create();
> > efd2 = epoll_create();
> > epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
> > epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
> >
> > When a packet arrives to the device underneath "dfd", the net code will
> > issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
> > callback wakeup entry on that queue, and the wake_up() performed by the
> > "dfd" net code will end up in ep_poll_callback(). At this point epoll
> > (efd1) notices that it may have some event ready, so it needs to wake up
> > the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
> > that ends up in another wake_up(), after having checked about the
> > recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
> > avoid stack blasting. Never hit the same queue, to avoid loops like:
> >
> > epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
> > epoll_ctl(efd3, EPOLL_CTL_ADD, efd2, ...);
> > epoll_ctl(efd4, EPOLL_CTL_ADD, efd3, ...);
> > epoll_ctl(efd1, EPOLL_CTL_ADD, efd4, ...);
> >
> > The code "if (tncur->wq == wq || ..." prevents re-entering the same
> > queue/lock.
>
> Since the epoll code is very careful to not nest same instance locks
> allow the recursion.
>
> Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
> ---
> fs/eventpoll.c |2 +-
> include/linux/wait.h | 16
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> Index: linux-2.6/fs/eventpoll.c
> ===
> --- linux-2.6.orig/fs/eventpoll.c
> +++ linux-2.6/fs/eventpoll.c
> @@ -353,7 +353,7 @@ static void ep_poll_safewake(struct poll
> spin_unlock_irqrestore(>lock, flags);
>
> /* Do really wake up now */
> - wake_up(wq);
> + wake_up_nested(wq, 1 + wake_nests);
>
> /* Remove the current task from the list */
> spin_lock_irqsave(>lock, flags);
> Index: linux-2.6/include/linux/wait.h
> ===
> --- linux-2.6.orig/include/linux/wait.h
> +++ linux-2.6/include/linux/wait.h
> @@ -161,6 +161,22 @@ wait_queue_head_t *FASTCALL(bit_waitqueu
> #define wake_up_locked(x) __wake_up_locked((x),
> TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE) #define
> wake_up_interruptible_sync(x) __wake_up_sync((x),
> TASK_INTERRUPTIBLE, 1)
>
> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> +/*
> + * macro to avoid include hell
> + */
> +#define wake_up_nested(x, s) \
> +do { \
> + unsigned long flags;\
> + \
> + spin_lock_irqsave_nested(&(x)->lock, flags, (s)); \
> + wake_up_locked(x); \
> + spin_unlock_irqrestore(&(x)->lock, flags); \
> +} while (0)
> +#else
> +#define wake_up_nested(x, s) wake_up(x)
> +#endif
> +
> #define __wait_event(wq, condition) \
> do { \
> DEFINE_WAIT(__wait);\
--
Denys Fedoryshchenko
Technical Manager
Virtual ISP S.A.L.
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Re: possible recursive locking, 2.6.24-rc7
On Sun, 2008-01-13 at 17:22 +0100, Peter Zijlstra wrote:
> On Sun, 2008-01-13 at 17:51 +0200, Denys Fedoryshchenko wrote:
> > Hi, got in dmesg
> > Not sure where to send (there is TCP), so sending netdev@ and kernel@
>
> It's epoll, this is a known issue and will be fixed soon. Thanks for
> reporting.
If its easy for you to reproduce, would you mind giving the following
patch a spin?
---
Subject: lockdep: annotate epoll
On Sat, 2008-01-05 at 13:35 -0800, Davide Libenzi wrote:
> I remember I talked with Arjan about this time ago. Basically, since 1)
> you can drop an epoll fd inside another epoll fd 2) callback-based wakeups
> are used, you can see a wake_up() from inside another wake_up(), but they
> will never refer to the same lock instance.
> Think about:
>
> dfd = socket(...);
> efd1 = epoll_create();
> efd2 = epoll_create();
> epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
> epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
>
> When a packet arrives to the device underneath "dfd", the net code will
> issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
> callback wakeup entry on that queue, and the wake_up() performed by the
> "dfd" net code will end up in ep_poll_callback(). At this point epoll
> (efd1) notices that it may have some event ready, so it needs to wake up
> the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
> that ends up in another wake_up(), after having checked about the
> recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
> avoid stack blasting. Never hit the same queue, to avoid loops like:
>
> epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
> epoll_ctl(efd3, EPOLL_CTL_ADD, efd2, ...);
> epoll_ctl(efd4, EPOLL_CTL_ADD, efd3, ...);
> epoll_ctl(efd1, EPOLL_CTL_ADD, efd4, ...);
>
> The code "if (tncur->wq == wq || ..." prevents re-entering the same
> queue/lock.
Since the epoll code is very careful to not nest same instance locks
allow the recursion.
Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
---
fs/eventpoll.c |2 +-
include/linux/wait.h | 16
2 files changed, 17 insertions(+), 1 deletion(-)
Index: linux-2.6/fs/eventpoll.c
===
--- linux-2.6.orig/fs/eventpoll.c
+++ linux-2.6/fs/eventpoll.c
@@ -353,7 +353,7 @@ static void ep_poll_safewake(struct poll
spin_unlock_irqrestore(>lock, flags);
/* Do really wake up now */
- wake_up(wq);
+ wake_up_nested(wq, 1 + wake_nests);
/* Remove the current task from the list */
spin_lock_irqsave(>lock, flags);
Index: linux-2.6/include/linux/wait.h
===
--- linux-2.6.orig/include/linux/wait.h
+++ linux-2.6/include/linux/wait.h
@@ -161,6 +161,22 @@ wait_queue_head_t *FASTCALL(bit_waitqueu
#definewake_up_locked(x) __wake_up_locked((x),
TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE)
#define wake_up_interruptible_sync(x) __wake_up_sync((x),TASK_INTERRUPTIBLE,
1)
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+/*
+ * macro to avoid include hell
+ */
+#define wake_up_nested(x, s) \
+do { \
+ unsigned long flags;\
+ \
+ spin_lock_irqsave_nested(&(x)->lock, flags, (s)); \
+ wake_up_locked(x); \
+ spin_unlock_irqrestore(&(x)->lock, flags); \
+} while (0)
+#else
+#define wake_up_nested(x, s) wake_up(x)
+#endif
+
#define __wait_event(wq, condition)\
do { \
DEFINE_WAIT(__wait);\
--
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Re: possible recursive locking, 2.6.24-rc7
On Sun, 2008-01-13 at 17:51 +0200, Denys Fedoryshchenko wrote:
> Hi, got in dmesg
> Not sure where to send (there is TCP), so sending netdev@ and kernel@
It's epoll, this is a known issue and will be fixed soon. Thanks for
reporting.
> [159859.491752]
> [159859.491755] =
> [159859.492021] [ INFO: possible recursive locking detected ]
> [159859.492156] 2.6.24-rc7-devel #2
> [159859.492284] -
> [159859.492418] swapper/0 is trying to acquire lock:
> [159859.492550] (>lock){++..}, at: [] __wake_up+0x15/0x42
> [159859.492883]
> [159859.492884] but task is already holding lock:
> [159859.493140] (>lock){++..}, at: [] __wake_up+0x15/0x42
> [159859.493466]
> [159859.493467] other info that might help us debug this:
> [159859.493726] 5 locks held by swapper/0:
> [159859.495687] #0: (rcu_read_lock){..--}, at: []
> netif_receive_skb+
> 0x9c/0x3a7
> [159859.496141] #1: (rcu_read_lock){..--}, at: []
> ip_local_deliver_f
> inish+0x30/0x18d
> [159859.496604] #2: (slock-AF_INET/1){-+..}, at: []
> tcp_v4_rcv+0x426
>/0x812
> [159859.497104] #3: (clock-AF_INET){-.-?}, at: []
> sock_def_readable+
> 0x18/0x6e
> [159859.497555] #4: (>lock){++..}, at: [] __wake_up+0x15/0x42
> [159859.497931]
> [159859.497932] stack backtrace:
> [159859.498185] Pid: 0, comm: swapper Not tainted 2.6.24-rc7-devel #2
> [159859.498320] [] show_trace_log_lvl+0x1a/0x2f
> [159859.498505] [] show_trace+0x12/0x14
> [159859.498690] [] dump_stack+0x6c/0x72
> [159859.498872] [] __lock_acquire+0x172/0xb8c
> [159859.499057] [] lock_acquire+0x5f/0x78
> [159859.499239] [] _spin_lock_irqsave+0x34/0x44
> [159859.499423] [] __wake_up+0x15/0x42
> [159859.499604] [] ep_poll_safewake+0x8e/0xbf
> [159859.499787] [] ep_poll_callback+0x9f/0xac
> [159859.499970] [] __wake_up_common+0x32/0x5c
> [159859.500154] [] __wake_up+0x31/0x42
> [159859.500335] [] sock_def_readable+0x42/0x6e
> [159859.500518] [] tcp_rcv_established+0x3bc/0x643
> [159859.500704] [] tcp_v4_do_rcv+0x2f/0x325
> [159859.500887] [] tcp_v4_rcv+0x7c9/0x812
> [159859.501069] [] ip_local_deliver_finish+0x107/0x18d
> [159859.501255] [] ip_local_deliver+0x72/0x7c
> [159859.501438] [] ip_rcv_finish+0x2cf/0x2ee
> [159859.501623] [] ip_rcv+0x211/0x23b
> [159859.501805] [] netif_receive_skb+0x350/0x3a7
> [159859.501989] [] bnx2_poll+0x975/0xb45 [bnx2]
> [159859.502177] [] net_rx_action+0x6c/0x116
> [159859.502360] [] __do_softirq+0x6f/0xe9
> [159859.502543] [] do_softirq+0x3a/0x52
> [159859.502728] [] irq_exit+0x47/0x7b
> [159859.502911] [] do_IRQ+0x81/0x96
> [159859.503098] [] common_interrupt+0x2e/0x34
> [159859.503288] [] mwait_idle+0x12/0x14
> [159859.503476] [] cpu_idle+0x7b/0x95
> [159859.503662] [] rest_init+0x49/0x4b
> [159859.503844] [] start_kernel+0x2f9/0x301
> [159859.504030] [<>] 0x0
> [159859.504210] ===
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To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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Re: possible recursive locking, 2.6.24-rc7
On Sun, 2008-01-13 at 17:51 +0200, Denys Fedoryshchenko wrote:
Hi, got in dmesg
Not sure where to send (there is TCP), so sending netdev@ and kernel@
It's epoll, this is a known issue and will be fixed soon. Thanks for
reporting.
[159859.491752]
[159859.491755] =
[159859.492021] [ INFO: possible recursive locking detected ]
[159859.492156] 2.6.24-rc7-devel #2
[159859.492284] -
[159859.492418] swapper/0 is trying to acquire lock:
[159859.492550] (q-lock){++..}, at: [c01175ff] __wake_up+0x15/0x42
[159859.492883]
[159859.492884] but task is already holding lock:
[159859.493140] (q-lock){++..}, at: [c01175ff] __wake_up+0x15/0x42
[159859.493466]
[159859.493467] other info that might help us debug this:
[159859.493726] 5 locks held by swapper/0:
[159859.495687] #0: (rcu_read_lock){..--}, at: [c02dd9af]
netif_receive_skb+
0x9c/0x3a7
[159859.496141] #1: (rcu_read_lock){..--}, at: [c02f8072]
ip_local_deliver_f
inish+0x30/0x18d
[159859.496604] #2: (slock-AF_INET/1){-+..}, at: [c0310474]
tcp_v4_rcv+0x426
/0x812
[159859.497104] #3: (clock-AF_INET){-.-?}, at: [c02d7684]
sock_def_readable+
0x18/0x6e
[159859.497555] #4: (q-lock){++..}, at: [c01175ff] __wake_up+0x15/0x42
[159859.497931]
[159859.497932] stack backtrace:
[159859.498185] Pid: 0, comm: swapper Not tainted 2.6.24-rc7-devel #2
[159859.498320] [c0105e68] show_trace_log_lvl+0x1a/0x2f
[159859.498505] [c0106810] show_trace+0x12/0x14
[159859.498690] [c0107107] dump_stack+0x6c/0x72
[159859.498872] [c01384c0] __lock_acquire+0x172/0xb8c
[159859.499057] [c01392a7] lock_acquire+0x5f/0x78
[159859.499239] [c03299cf] _spin_lock_irqsave+0x34/0x44
[159859.499423] [c01175ff] __wake_up+0x15/0x42
[159859.499604] [c01869ea] ep_poll_safewake+0x8e/0xbf
[159859.499787] [c01876b3] ep_poll_callback+0x9f/0xac
[159859.499970] [c0115d36] __wake_up_common+0x32/0x5c
[159859.500154] [c011761b] __wake_up+0x31/0x42
[159859.500335] [c02d76ae] sock_def_readable+0x42/0x6e
[159859.500518] [c0309105] tcp_rcv_established+0x3bc/0x643
[159859.500704] [c030e588] tcp_v4_do_rcv+0x2f/0x325
[159859.500887] [c0310817] tcp_v4_rcv+0x7c9/0x812
[159859.501069] [c02f8149] ip_local_deliver_finish+0x107/0x18d
[159859.501255] [c02f854e] ip_local_deliver+0x72/0x7c
[159859.501438] [c02f8023] ip_rcv_finish+0x2cf/0x2ee
[159859.501623] [c02f84b2] ip_rcv+0x211/0x23b
[159859.501805] [c02ddc63] netif_receive_skb+0x350/0x3a7
[159859.501989] [f88f2b6d] bnx2_poll+0x975/0xb45 [bnx2]
[159859.502177] [c02dfdab] net_rx_action+0x6c/0x116
[159859.502360] [c0120ed8] __do_softirq+0x6f/0xe9
[159859.502543] [c0120f8c] do_softirq+0x3a/0x52
[159859.502728] [c012128b] irq_exit+0x47/0x7b
[159859.502911] [c01076af] do_IRQ+0x81/0x96
[159859.503098] [c010586a] common_interrupt+0x2e/0x34
[159859.503288] [c0103434] mwait_idle+0x12/0x14
[159859.503476] [c010353d] cpu_idle+0x7b/0x95
[159859.503662] [c03272c9] rest_init+0x49/0x4b
[159859.503844] [c0449c08] start_kernel+0x2f9/0x301
[159859.504030] [] 0x0
[159859.504210] ===
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To unsubscribe from this list: send the line unsubscribe linux-kernel in
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More majordomo info at http://vger.kernel.org/majordomo-info.html
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Re: possible recursive locking, 2.6.24-rc7
On Sun, 2008-01-13 at 17:22 +0100, Peter Zijlstra wrote:
On Sun, 2008-01-13 at 17:51 +0200, Denys Fedoryshchenko wrote:
Hi, got in dmesg
Not sure where to send (there is TCP), so sending netdev@ and kernel@
It's epoll, this is a known issue and will be fixed soon. Thanks for
reporting.
If its easy for you to reproduce, would you mind giving the following
patch a spin?
---
Subject: lockdep: annotate epoll
On Sat, 2008-01-05 at 13:35 -0800, Davide Libenzi wrote:
I remember I talked with Arjan about this time ago. Basically, since 1)
you can drop an epoll fd inside another epoll fd 2) callback-based wakeups
are used, you can see a wake_up() from inside another wake_up(), but they
will never refer to the same lock instance.
Think about:
dfd = socket(...);
efd1 = epoll_create();
efd2 = epoll_create();
epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
When a packet arrives to the device underneath dfd, the net code will
issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
callback wakeup entry on that queue, and the wake_up() performed by the
dfd net code will end up in ep_poll_callback(). At this point epoll
(efd1) notices that it may have some event ready, so it needs to wake up
the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
that ends up in another wake_up(), after having checked about the
recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
avoid stack blasting. Never hit the same queue, to avoid loops like:
epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
epoll_ctl(efd3, EPOLL_CTL_ADD, efd2, ...);
epoll_ctl(efd4, EPOLL_CTL_ADD, efd3, ...);
epoll_ctl(efd1, EPOLL_CTL_ADD, efd4, ...);
The code if (tncur-wq == wq || ... prevents re-entering the same
queue/lock.
Since the epoll code is very careful to not nest same instance locks
allow the recursion.
Signed-off-by: Peter Zijlstra [EMAIL PROTECTED]
---
fs/eventpoll.c |2 +-
include/linux/wait.h | 16
2 files changed, 17 insertions(+), 1 deletion(-)
Index: linux-2.6/fs/eventpoll.c
===
--- linux-2.6.orig/fs/eventpoll.c
+++ linux-2.6/fs/eventpoll.c
@@ -353,7 +353,7 @@ static void ep_poll_safewake(struct poll
spin_unlock_irqrestore(psw-lock, flags);
/* Do really wake up now */
- wake_up(wq);
+ wake_up_nested(wq, 1 + wake_nests);
/* Remove the current task from the list */
spin_lock_irqsave(psw-lock, flags);
Index: linux-2.6/include/linux/wait.h
===
--- linux-2.6.orig/include/linux/wait.h
+++ linux-2.6/include/linux/wait.h
@@ -161,6 +161,22 @@ wait_queue_head_t *FASTCALL(bit_waitqueu
#definewake_up_locked(x) __wake_up_locked((x),
TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE)
#define wake_up_interruptible_sync(x) __wake_up_sync((x),TASK_INTERRUPTIBLE,
1)
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+/*
+ * macro to avoid include hell
+ */
+#define wake_up_nested(x, s) \
+do { \
+ unsigned long flags;\
+ \
+ spin_lock_irqsave_nested((x)-lock, flags, (s)); \
+ wake_up_locked(x); \
+ spin_unlock_irqrestore((x)-lock, flags); \
+} while (0)
+#else
+#define wake_up_nested(x, s) wake_up(x)
+#endif
+
#define __wait_event(wq, condition)\
do { \
DEFINE_WAIT(__wait);\
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Re: possible recursive locking, 2.6.24-rc7
I cannot reproduce, it is happened with rtorrent just randomly. But i will
patch and keep watching.
On Sun, 13 Jan 2008 19:44:26 +0100, Peter Zijlstra wrote
On Sun, 2008-01-13 at 17:22 +0100, Peter Zijlstra wrote:
On Sun, 2008-01-13 at 17:51 +0200, Denys Fedoryshchenko wrote:
Hi, got in dmesg
Not sure where to send (there is TCP), so sending netdev@ and kernel@
It's epoll, this is a known issue and will be fixed soon. Thanks for
reporting.
If its easy for you to reproduce, would you mind giving the following
patch a spin?
---
Subject: lockdep: annotate epoll
On Sat, 2008-01-05 at 13:35 -0800, Davide Libenzi wrote:
I remember I talked with Arjan about this time ago. Basically, since 1)
you can drop an epoll fd inside another epoll fd 2) callback-based wakeups
are used, you can see a wake_up() from inside another wake_up(), but they
will never refer to the same lock instance.
Think about:
dfd = socket(...);
efd1 = epoll_create();
efd2 = epoll_create();
epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
When a packet arrives to the device underneath dfd, the net code will
issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
callback wakeup entry on that queue, and the wake_up() performed by the
dfd net code will end up in ep_poll_callback(). At this point epoll
(efd1) notices that it may have some event ready, so it needs to wake up
the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
that ends up in another wake_up(), after having checked about the
recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
avoid stack blasting. Never hit the same queue, to avoid loops like:
epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
epoll_ctl(efd3, EPOLL_CTL_ADD, efd2, ...);
epoll_ctl(efd4, EPOLL_CTL_ADD, efd3, ...);
epoll_ctl(efd1, EPOLL_CTL_ADD, efd4, ...);
The code if (tncur-wq == wq || ... prevents re-entering the same
queue/lock.
Since the epoll code is very careful to not nest same instance locks
allow the recursion.
Signed-off-by: Peter Zijlstra [EMAIL PROTECTED]
---
fs/eventpoll.c |2 +-
include/linux/wait.h | 16
2 files changed, 17 insertions(+), 1 deletion(-)
Index: linux-2.6/fs/eventpoll.c
===
--- linux-2.6.orig/fs/eventpoll.c
+++ linux-2.6/fs/eventpoll.c
@@ -353,7 +353,7 @@ static void ep_poll_safewake(struct poll
spin_unlock_irqrestore(psw-lock, flags);
/* Do really wake up now */
- wake_up(wq);
+ wake_up_nested(wq, 1 + wake_nests);
/* Remove the current task from the list */
spin_lock_irqsave(psw-lock, flags);
Index: linux-2.6/include/linux/wait.h
===
--- linux-2.6.orig/include/linux/wait.h
+++ linux-2.6/include/linux/wait.h
@@ -161,6 +161,22 @@ wait_queue_head_t *FASTCALL(bit_waitqueu
#define wake_up_locked(x) __wake_up_locked((x),
TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE) #define
wake_up_interruptible_sync(x) __wake_up_sync((x),
TASK_INTERRUPTIBLE, 1)
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+/*
+ * macro to avoid include hell
+ */
+#define wake_up_nested(x, s) \
+do { \
+ unsigned long flags;\
+ \
+ spin_lock_irqsave_nested((x)-lock, flags, (s)); \
+ wake_up_locked(x); \
+ spin_unlock_irqrestore((x)-lock, flags); \
+} while (0)
+#else
+#define wake_up_nested(x, s) wake_up(x)
+#endif
+
#define __wait_event(wq, condition) \
do { \
DEFINE_WAIT(__wait);\
--
Denys Fedoryshchenko
Technical Manager
Virtual ISP S.A.L.
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