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From: Zoltan Menyhart <Zoltan.Menyhart@bull.net>
To: linux-ia64@vger.kernel.org
Subject: SAL calling conventions + locking
Date: Fri, 09 Dec 2005 16:42:22 +0000	[thread overview]
Message-ID: <4399B3EE.6050408@bull.net> (raw)

The SAL specification does say that the SAL procedures should be called
with interrupts enabled if we call them in virtual mode.

Here is the simplified CPEI handler control flow:

ia64_mca_cpe_int_handler():

	/* SAL spec states this should run w/ interrupts enabled */
	local_irq_enable();
	ia64_mca_log_sal_error_record(SAL_INFO_TYPE_CPE):

		ia64_log_get():

			IA64_LOG_LOCK():

				spin_lock_irqsave():

			ia64_sal_get_state_info();
			IA64_LOG_UNLOCK()

		salinfo_log_wakeup()
		if (rh->severity = sal_log_severity_corrected)
			ia64_sal_clear_state_info();

Despite the note "SAL spec ... w/ interrupts enabled" the interrupts
are disabled before "ia64_sal_get_state_info()" is invoked.

Can someone please tell me:
- why the spec. requires to call the SAL with interrupts enabled,
- why Linux calls the SAL with interrupts disabled,
- what happens if the SAL is called with interrupts disabled?

The second issue is:
The lock of the log is released before "salinfo_log_wakeup()" could record
the existence of the current log. Two more logs can arrive and overwrite
the current log without even indicting the loss of the information.
(E.g. CPEI-s with interrupt redirection, CMCI-s on multiple CPUs.)
Should not we keep the log lock at least while "salinfo_log_wakeup()"
executes?

Thanks.

Zoltan Menyhart

             reply	other threads:[~2005-12-09 16:42 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-12-09 16:42 Zoltan Menyhart [this message]
2005-12-09 17:03 ` SAL calling conventions + locking Luck, Tony

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