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List:       linux-api
Subject:    Is perf_sigtrap synchronous?
From:       ebiederm () xmission ! com (Eric W !  Biederman)
Date:       2021-04-30 23:23:51
Message-ID: m1im43qrug.fsf_-_ () fess ! ebiederm ! org
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I am looking at perf_sigtrap and I am confused by the code.


	/*
	 * We'd expect this to only occur if the irq_work is delayed and either
	 * ctx->task or current has changed in the meantime. This can be the
	 * case on architectures that do not implement arch_irq_work_raise().
	 */
	if (WARN_ON_ONCE(event->ctx->task != current))
		return;

	/*
	 * perf_pending_event() can race with the task exiting.
	 */
	if (current->flags & PF_EXITING)
		return;


It performs tests that absolutely can never fail if we are talking about
a synchronous exception.  The code force_sig family of functions only
make sense to use with and are only safe to use with synchronous
exceptions.

Are the tests in perf_sigtrap necessary or is perf_sigtrap not reporting
a synchronous event?

Eric
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