On Monday, November 19, 2012 09:10:58 AM Rafael J. Wysocki wrote: > On Tuesday, November 06, 2012 08:02:06 AM Toshi Kani wrote: > > This patch introduces acpi_pr_<level>(), where <level> is a kernel > > message level such as err/warn/info, to support improved logging > > messages for ACPI, esp. for hotplug operations. acpi_pr_<level>() > > appends "ACPI" prefix and ACPI object path to the messages. This > > improves diagnosis of hotplug operations since an error message in > > a log file identifies an object that caused an issue. > > > > acpi_pr_<level>() takes acpi_handle as an argument, which is passed > > to ACPI hotplug notify handlers from the ACPICA. Therefore, it is > > always available unlike other kernel objects, such as device. > > > > For example: > > acpi_pr_err(handle, "Device don't exist, dropping EJECT\n"); > > logs an error message like this at KERN_ERR. > > ACPI: \_SB_.SCK4.CPU4: Device don't exist, dropping EJECT > > > > ACPI drivers can use acpi_pr_<level>() when they need to identify > > a target ACPI object path in their messages, such as error cases. > > The usage model is similar to dev_<level>(). acpi_pr_<level>() can > > be used when device is not created/valid, which may be the case in > > ACPI hotplug handlers. ACPI object path is also consistent on the > > platform, unlike device name that changes over hotplug operations. > > > > ACPI drivers should use dev_<level>() when device is valid and > > acpi_pr_<level>() is already used by the caller in its error path. > > Device name provides more user friendly information. > > > > ACPI drivers also continue to use pr_<level>() when messages do not > > need to specify device information, such as boot-up messages. > > > > Note: ACPI_[WARNING|INFO|ERROR]() are intended for the ACPICA and > > are not associated with the kernel message level. > > Well, the idea is generally good, but unfortunately acpi_get_name() is > not a cheap operation. Namely, it takes the global namespace mutex, > so your acpi_printk() may be a source of serious contention on that > lock if used excessively from concurrent threads. > > Do you think you can address this problem? > > Moreover, this also means that acpi_printk() cannot be used from interrupt > context, so it is not a printk() replacement, which at least should be > documented. Unfortunately, I lost your reply to my previous message in this thread due to my e-mail client malfunction. Sorry about that. What about calling them acpi_handle_printk() and acpi_handle_<level>, respectively? Then, if it is clearly documented that those things acquire the global namespace mutex and are not suitable for interrupt context, it should be OK. And please take Joe's feedback into account. :-) Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
