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Revision 9107c89e269d2738019861bb518e3d59bef01781 authored by Peter Zijlstra on 24 February 2016, 17:45:45 UTC, committed by Ingo Molnar on 25 February 2016, 07:42:34 UTC 
perf: Fix race between event install and jump_labels
 
perf_install_in_context() relies upon the context switch hooks to have
scheduled in events when the IPI misses its target -- after all, if
the task has moved from the CPU (or wasn't running at all), it will
have to context switch to run elsewhere.

This however doesn't appear to be happening.

It is possible for the IPI to not happen (task wasn't running) only to
later observe the task running with an inactive context.

The only possible explanation is that the context switch hooks are not
called. Therefore put in a sync_sched() after toggling the jump_label
to guarantee all CPUs will have them enabled before we install an
event.

A simple if (0->1) sync_sched() will not in fact work, because any
further increment can race and complete before the sync_sched().
Therefore we must jump through some hoops.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174947.980211985@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 parent a69b0ca
Raw File
Kconfig 
config UDF_FS
	tristate "UDF file system support"
	select CRC_ITU_T
	help
	  This is a file system used on some CD-ROMs and DVDs. Since the
	  file system is supported by multiple operating systems and is more
	  compatible with standard unix file systems, it is also suitable for
	  removable USB disks. Say Y if you intend to mount DVD discs or CDRW's
	  written in packet mode, or if you want to use UDF for removable USB
	  disks. Please read <file:Documentation/filesystems/udf.txt>.

	  To compile this file system support as a module, choose M here: the
	  module will be called udf.

	  If unsure, say N.

config UDF_NLS
	bool
	default y
	depends on (UDF_FS=m && NLS) || (UDF_FS=y && NLS=y)
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