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authorKay Sievers <kay@vrfy.org>2012-05-03 02:29:41 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-05-07 17:03:27 -0700
commite11fea92e13fb91c50bacca799a6131c81929986 (patch)
tree3b9204f4eccc6b488b843d6d00e65dc982c50160 /include/linux/printk.h
parent7ff9554bb578ba02166071d2d487b7fc7d860d62 (diff)
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 <kzak@redhat.com> Tested-by: William Douglas <william.douglas@intel.com> Signed-off-by: Kay Sievers <kay@vrfy.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/printk.h')
-rw-r--r--include/linux/printk.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/printk.h b/include/linux/printk.h
index aa3c66da105..1bec2f7a2d4 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,