From e11fea92e13fb91c50bacca799a6131c81929986 Mon Sep 17 00:00:00 2001 From: Kay Sievers Date: Thu, 3 May 2012 02:29:41 +0200 Subject: kmsg: export printk records to the /dev/kmsg interface Support for multiple concurrent readers of /dev/kmsg, with read(), seek(), poll() support. Output of message sequence numbers, to allow userspace log consumers to reliably reconnect and reconstruct their state at any given time. After open("/dev/kmsg"), read() always returns *all* buffered records. If only future messages should be read, SEEK_END can be used. In case records get overwritten while /dev/kmsg is held open, or records get faster overwritten than they are read, the next read() will return -EPIPE and the current reading position gets updated to the next available record. The passed sequence numbers allow the log consumer to calculate the amount of lost messages. [root@mop ~]# cat /dev/kmsg 5,0,0;Linux version 3.4.0-rc1+ (kay@mop) (gcc version 4.7.0 20120315 ... 6,159,423091;ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff]) 7,160,424069;pci_root PNP0A03:00: host bridge window [io 0x0000-0x0cf7] (ignored) SUBSYSTEM=acpi DEVICE=+acpi:PNP0A03:00 6,339,5140900;NET: Registered protocol family 10 30,340,5690716;udevd[80]: starting version 181 6,341,6081421;FDC 0 is a S82078B 6,345,6154686;microcode: CPU0 sig=0x623, pf=0x0, revision=0x0 7,346,6156968;sr 1:0:0:0: Attached scsi CD-ROM sr0 SUBSYSTEM=scsi DEVICE=+scsi:1:0:0:0 6,347,6289375;microcode: CPU1 sig=0x623, pf=0x0, revision=0x0 Cc: Karel Zak Tested-by: William Douglas Signed-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman --- include/linux/printk.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/printk.h') diff --git a/include/linux/printk.h b/include/linux/printk.h index aa3c66d..1bec2f7 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -300,6 +300,8 @@ extern void dump_stack(void) __cold; no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) #endif +extern const struct file_operations kmsg_fops; + enum { DUMP_PREFIX_NONE, DUMP_PREFIX_ADDRESS, -- cgit v1.1