Commit 1e259e0a authored Feb 28, 2010 by Frederic Weisbecker

hw-breakpoints: Remove stub unthrottle callback



We support event unthrottling in breakpoint events. It means
that if we have more than sysctl_perf_event_sample_rate/HZ,
perf will throttle, ignoring subsequent events until the next
tick.

So if ptrace exceeds this max rate, it will omit events, which
breaks the ptrace determinism that is supposed to report every
triggered breakpoints. This is likely to happen if we set
sysctl_perf_event_sample_rate to 1.

This patch removes support for unthrottling in breakpoint
events to break throttling and restore ptrace determinism.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: 2.6.33.x <stable@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>

parent 388c3aab

arch/x86/kernel/hw_breakpoint.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -531,8 +531,3 @@ void hw_breakpoint_pmu_read(struct perf_event *bp)
		{
		/* TODO */
		}

		void hw_breakpoint_pmu_unthrottle(struct perf_event *bp)
		{
		/* TODO */
		}

kernel/hw_breakpoint.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -489,5 +489,4 @@ struct pmu perf_ops_bp = {
		.enable = arch_install_hw_breakpoint,
		.disable = arch_uninstall_hw_breakpoint,
		.read = hw_breakpoint_pmu_read,
		.unthrottle = hw_breakpoint_pmu_unthrottle
		};

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