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Date: Tue, 26 Aug 2008 13:03:21 -0700 From: Daniel Walker <dwalker@...sta.com> To: Matthew Wilcox <matthew@....cx> Cc: Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>, Len Brown <len.brown@...el.com>, Robert Moore <robert.moore@...el.com>, linux-acpi@...r.kernel.org Subject: Re: [PATCH 4/4] acpi: semaphore removal On Tue, 2008-08-26 at 13:50 -0600, Matthew Wilcox wrote: > On Tue, Aug 26, 2008 at 12:30:46PM -0700, Daniel Walker wrote: > > On Tue, 2008-08-26 at 13:13 -0600, Matthew Wilcox wrote: > > > On Tue, Aug 26, 2008 at 11:59:49AM -0700, Daniel Walker wrote: > > > > The semaphore usage in ACPI is more like completions. The ASL > > > > > > Huh? They are semaphores. They're not 'more like completions' at all. > > > > You can clearly make a completion out of a semaphore, but we have a > > completion API .. ACPI is using locked semaphores, and essentially > > re-making completions with the semaphore API.. > > What makes you think that? > > executer/excreate.c: status = acpi_os_create_semaphore(ACPI_NO_UNIT_LIMIT, 0, > executer/exsystem.c: acpi_os_create_semaphore(ACPI_NO_UNIT_LIMIT, 0, &temp_semaphore); > namespace/nsaccess.c: acpi_os_create_semaphore(1, 0, > osl.c:acpi_os_create_semaphore(u32 max_units, u32 initial_units, acpi_handle * handle) > > All users set 'initial_units' to 0. > We have from ACPI, acpi_status acpi_os_create_semaphore(u32 max_units, u32 initial_units, acpi_handle * handle) { struct semaphore *sem = NULL; ... sema_init(sem, initial_units); Then from semaphore.h, #define init_MUTEX(sem) sema_init(sem, 1) #define init_MUTEX_LOCKED(sem) sema_init(sem, 0) So initial units of 0 means make it locked initially .. Initialize to 1 would be a regular unlocked mutex .. Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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