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From: Peter Zijlstra <peterz@infradead.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
	Randy Dunlap <rdunlap@xenotime.net>,
	Arnaldo Carvalho de Melo <acme@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Christoph Hellwig <hch@infradead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
	Oleg Nesterov <oleg@redhat.com>, Mark Wielaard <mjw@redhat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Naren A Devaiah <naren.devaiah@in.ibm.com>,
	Jim Keniston <jkenisto@linux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	"Frank Ch. Eigler" <fche@redhat.com>,
	Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCHv11 2.6.36-rc2-tip 3/15]  3: uprobes: Slot allocation for Execution out of line(XOL)
Date: Fri, 03 Sep 2010 18:51:54 +0200	[thread overview]
Message-ID: <1283532714.2050.244.camel@laptop> (raw)
In-Reply-To: <20100903164010.GA1904@linux.vnet.ibm.com>

On Fri, 2010-09-03 at 22:10 +0530, Srikar Dronamraju wrote:
> > > +   mb();
> > 
> > Where is the matching barrier?
> 
> I dont want the compiler to reorder the instructions and do the
> assignment for user_bkpt to be done before we complete the copy above.
> 
> If the assignment happens before we copy the content into the slot,
> someother thread that might hit the same probe actually things the slot
> is ready and tries to jump to that slot even before the slot is
> initialized.
> 
> Please let me know if I could have done it differently. 


If you want a compiler barrier, use barrier(), but here you seem to
describe a multi-threaded situation, in which case the observer thread
needs at least a rmb() in order for that mb() to mean anything other
than the compiler barrier it implies.

Also, use smp_* barriers.



  reply	other threads:[~2010-09-03 16:52 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-25 13:41 [PATCHv11 2.6.36-rc2-tip 0/15] 0: Uprobes Patches Srikar Dronamraju
2010-08-25 13:41 ` [PATCHv11 2.6.36-rc2-tip 1/15] 1: mm: Move replace_page() / write_protect_page() to mm/memory.c Srikar Dronamraju
2010-08-25 13:41 ` [PATCHv11 2.6.36-rc2-tip 2/15] 2: uprobes: Breakpoint insertion/removal in user space applications Srikar Dronamraju
2010-09-01 19:38   ` Peter Zijlstra
2010-08-25 13:41 ` [PATCHv11 2.6.36-rc2-tip 3/15] 3: uprobes: Slot allocation for Execution out of line(XOL) Srikar Dronamraju
2010-09-01 20:13   ` Peter Zijlstra
2010-09-03 16:40     ` Srikar Dronamraju
2010-09-03 16:51       ` Peter Zijlstra [this message]
2010-09-03 17:26         ` Srikar Dronamraju
2010-09-03 17:41           ` Peter Zijlstra
2010-09-06  5:38             ` Srikar Dronamraju
2010-09-03 17:25       ` Peter Zijlstra
2010-09-02  8:23   ` Peter Zijlstra
2010-09-02 17:47     ` Srikar Dronamraju
2010-09-03  7:26       ` Peter Zijlstra
2010-09-06 17:59         ` Srikar Dronamraju
2010-09-06 18:20           ` Peter Zijlstra
2010-09-06 18:28           ` Peter Zijlstra
2010-08-25 13:42 ` [PATCHv11 2.6.36-rc2-tip 4/15] 4: uprobes: x86 specific functions for user space breakpointing Srikar Dronamraju
2010-09-03 10:26   ` Andi Kleen
2010-09-03 17:48     ` Srikar Dronamraju
2010-09-03 18:00       ` Peter Zijlstra
2010-09-06  7:53       ` Andi Kleen
2010-09-06 13:44         ` Srikar Dronamraju
2010-09-06 14:16           ` Andi Kleen
2010-09-07  0:56           ` Masami Hiramatsu
2010-08-25 13:42 ` [PATCHv11 2.6.36-rc2-tip 5/15] 5: uprobes: Uprobes (un)registration and exception handling Srikar Dronamraju
2010-09-01 21:43   ` Peter Zijlstra
2010-09-02  8:12     ` Peter Zijlstra
2010-09-03 16:42     ` Srikar Dronamraju
2010-09-03 17:19       ` Peter Zijlstra
2010-09-06 17:46         ` Srikar Dronamraju
2010-09-06 18:15           ` Peter Zijlstra
2010-09-06 18:15           ` Peter Zijlstra
2010-09-07  6:48             ` Srikar Dronamraju
2010-09-07  9:33               ` Peter Zijlstra
2010-09-07 11:51                 ` Srikar Dronamraju
2010-09-07 12:25                   ` Peter Zijlstra
2010-09-06 18:25           ` Mathieu Desnoyers
2010-09-06 20:40           ` Christoph Hellwig
2010-09-06 21:06             ` Peter Zijlstra
2010-09-06 21:12               ` Christoph Hellwig
2010-09-06 21:18                 ` Peter Zijlstra
2010-09-07 12:02             ` Srikar Dronamraju
2010-09-07 16:47               ` Mathieu Desnoyers
2010-09-03 17:27       ` Peter Zijlstra
2010-09-01 21:46   ` Peter Zijlstra
2010-08-25 13:42 ` [PATCHv11 2.6.36-rc2-tip 6/15] 6: uprobes: X86 support for Uprobes Srikar Dronamraju
2010-08-25 13:42 ` [PATCHv11 2.6.36-rc2-tip 7/15] 7: uprobes: Uprobes Documentation Srikar Dronamraju
2010-08-25 13:42 ` [PATCHv11 2.6.36-rc2-tip 8/15] 8: tracing: Extract out common code for kprobes/uprobes traceevents Srikar Dronamraju
2010-08-25 13:43 ` [PATCHv11 2.6.36-rc2-tip 9/15] 9: tracing: uprobes trace_event interface Srikar Dronamraju
2010-08-25 13:43 ` [PATCHv11 2.6.36-rc2-tip 10/15] 10: tracing: config option to enable both kprobe-tracer and uprobe-tracer Srikar Dronamraju
2010-08-26  6:02   ` Masami Hiramatsu
2010-08-27  9:31     ` Srikar Dronamraju
2010-08-27 11:04       ` Masami Hiramatsu
2010-08-27 12:17         ` Srikar Dronamraju
2010-08-27 15:37           ` Masami Hiramatsu
2010-08-27 14:10     ` [PATCHv11a " Srikar Dronamraju
2010-08-25 13:43 ` [PATCHv11 2.6.36-rc2-tip 11/15] 11: perf: list symbols in a dso in ascending order Srikar Dronamraju
2010-08-25 23:21   ` Arnaldo Carvalho de Melo
2010-08-26  4:32     ` Srikar Dronamraju
2010-08-30  8:35   ` [tip:perf/core] perf symbols: List symbols in a dso in ascending name order tip-bot for Srikar Dronamraju
2010-08-25 13:43 ` [PATCHv11 2.6.36-rc2-tip 12/15] 12: perf: show possible probes in a given file Srikar Dronamraju
2010-08-27 14:21   ` [PATCHv11a " Srikar Dronamraju
2010-10-20  9:56     ` Masami Hiramatsu
2010-08-25 13:43 ` [PATCHv11 2.6.36-rc2-tip 13/15] 13: perf: Loop thro each of the maps in a map_group Srikar Dronamraju
2010-08-25 13:44 ` [PATCHv11 2.6.36-rc2-tip 14/15] 14: perf: perf interface for uprobes Srikar Dronamraju
2010-08-25 13:44 ` [PATCHv11 2.6.36-rc2-tip 15/15] 15: perf: Show Potential probe points Srikar Dronamraju
2010-10-29  9:23 ` [PATCHv11 2.6.36-rc2-tip 0/15] 0: Uprobes Patches Christoph Hellwig
2010-10-29 10:48   ` Srikar Dronamraju
2010-11-04 18:45     ` Christoph Hellwig

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