From: Peter Zijlstra <peterz@infradead.org>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Waiman Long <waiman.long@hp.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Andrew Morton <akpm@linux-foundation.org>,
Richard Weinberger <richard@nod.at>,
Catalin Marinas <catalin.marinas@arm.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Matt Fleming <matt.fleming@intel.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Akinobu Mita <akinobu.mita@gmail.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Michel Lespinasse <walken@google.com>,
Andi Kleen <andi@firstfloor.org>, Rik van Riel <riel@redhat.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
George Spelvin <linux@horizon.com>, Harvey Harrison <harvey.ha>
Subject: Re: [PATCH RFC 1/2] qspinlock: Introducing a 4-byte queue spinlock implementation
Date: Thu, 1 Aug 2013 22:10:18 +0200 [thread overview]
Message-ID: <20130801201018.GR3008@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <51FAA5F8.2070209@linux.vnet.ibm.com>
On Thu, Aug 01, 2013 at 11:46:24PM +0530, Raghavendra K T wrote:
> On 08/01/2013 11:28 PM, Waiman Long wrote:
> >On 08/01/2013 05:40 AM, Peter Zijlstra wrote:
> >>On Wed, Jul 31, 2013 at 10:37:10PM -0400, Waiman Long wrote:
> >>
> [...]
> >>
> >>>+ */
> >>>+ for (qn_idx = 1; qn_idx< MAX_QNODES; qn_idx++) {
> >>>+ if (!node[qn_idx].used)
> >>>+ break;
> >> }
> >>
> >>>+ if (unlikely(qn_idx == MAX_QNODES)) {
> >>>+ /*
> >>>+ * This shouldn't happen, print a warning message
> >>>+ *& busy spinning on the lock.
> >>>+ */
> >>>+ pr_warn("qspinlock: queue node table exhausted at "
> >>>+ "cpu %d!\n", cpu_nr);
> >>This could make your machine die hard.. not all contexts can printk().
> >
> >Do you have any suggestion? I could skip the warning and silently do the
> >busy spinning. I just want some way to notify the user of this rare event.
>
> We have used debugfs in pv-spinlock to avoid that since printk uses
> spinlock again. may be it will help to profile many other parts of
> code too.
I always use early_printk(), but that requires you set up your serial
console properly and joe-user won't have done that.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Waiman Long <waiman.long@hp.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Andrew Morton <akpm@linux-foundation.org>,
Richard Weinberger <richard@nod.at>,
Catalin Marinas <catalin.marinas@arm.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Matt Fleming <matt.fleming@intel.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Akinobu Mita <akinobu.mita@gmail.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Michel Lespinasse <walken@google.com>,
Andi Kleen <andi@firstfloor.org>, Rik van Riel <riel@redhat.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
George Spelvin <linux@horizon.com>,
Harvey Harrison <harvey.harrison@gmail.com>,
"Chandramouleeswaran, Aswin" <aswin@hp.com>,
"Norton, Scott J" <scott.norton@hp.com>
Subject: Re: [PATCH RFC 1/2] qspinlock: Introducing a 4-byte queue spinlock implementation
Date: Thu, 1 Aug 2013 22:10:18 +0200 [thread overview]
Message-ID: <20130801201018.GR3008@twins.programming.kicks-ass.net> (raw)
Message-ID: <20130801201018.HI6JOB-Nk_WSwJn8ndWoORya0f7vKuZgJNAGENwR6zU@z> (raw)
In-Reply-To: <51FAA5F8.2070209@linux.vnet.ibm.com>
On Thu, Aug 01, 2013 at 11:46:24PM +0530, Raghavendra K T wrote:
> On 08/01/2013 11:28 PM, Waiman Long wrote:
> >On 08/01/2013 05:40 AM, Peter Zijlstra wrote:
> >>On Wed, Jul 31, 2013 at 10:37:10PM -0400, Waiman Long wrote:
> >>
> [...]
> >>
> >>>+ */
> >>>+ for (qn_idx = 1; qn_idx< MAX_QNODES; qn_idx++) {
> >>>+ if (!node[qn_idx].used)
> >>>+ break;
> >> }
> >>
> >>>+ if (unlikely(qn_idx == MAX_QNODES)) {
> >>>+ /*
> >>>+ * This shouldn't happen, print a warning message
> >>>+ *& busy spinning on the lock.
> >>>+ */
> >>>+ pr_warn("qspinlock: queue node table exhausted at "
> >>>+ "cpu %d!\n", cpu_nr);
> >>This could make your machine die hard.. not all contexts can printk().
> >
> >Do you have any suggestion? I could skip the warning and silently do the
> >busy spinning. I just want some way to notify the user of this rare event.
>
> We have used debugfs in pv-spinlock to avoid that since printk uses
> spinlock again. may be it will help to profile many other parts of
> code too.
I always use early_printk(), but that requires you set up your serial
console properly and joe-user won't have done that.
next prev parent reply other threads:[~2013-08-01 20:10 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1375324631-32868-1-git-send-email-Waiman.Long@hp.com>
2013-08-01 2:37 ` [PATCH RFC 1/2] qspinlock: Introducing a 4-byte queue spinlock implementation Waiman Long
2013-08-01 2:37 ` Waiman Long
[not found] ` <20130801094029.GK3008@twins.programming.kicks-ass.net>
2013-08-01 10:11 ` Raghavendra K T
2013-08-01 10:11 ` Raghavendra K T
2013-08-01 10:12 ` Peter Zijlstra
2013-08-01 10:12 ` Peter Zijlstra
2013-08-01 10:14 ` Peter Zijlstra
2013-08-01 10:14 ` Peter Zijlstra
[not found] ` <51FAA1C3.2050507@hp.com>
2013-08-01 18:16 ` Raghavendra K T
2013-08-01 18:16 ` Raghavendra K T
2013-08-01 20:10 ` Peter Zijlstra [this message]
2013-08-01 20:10 ` Peter Zijlstra
2013-08-01 20:36 ` Raghavendra K T
2013-08-01 20:36 ` Raghavendra K T
2013-08-01 20:23 ` Raghavendra K T
2013-08-01 20:23 ` Raghavendra K T
2013-08-01 20:47 ` Peter Zijlstra
2013-08-01 20:47 ` Peter Zijlstra
2013-08-02 2:54 ` Raghavendra K T
2013-08-02 2:54 ` Raghavendra K T
2013-08-01 21:09 ` Waiman Long
2013-08-01 21:09 ` Waiman Long
2013-08-02 3:00 ` Raghavendra K T
2013-08-02 3:00 ` Raghavendra K T
2013-08-01 2:37 ` [PATCH RFC 2/2] qspinlock x86: Enable x86 to use queue spinlock Waiman Long
2013-08-01 2:37 ` Waiman Long
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