proc.5: Document /proc/sys/vm/memory_failure_early_kill

New in 2.6.32. Description based on the text in
Documentation/sysctl/vm.txt.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/man5/proc.5 b/man5/proc.5
index c8dadef5..8ebd5992 100644
--- a/man5/proc.5
+++ b/man5/proc.5
@@ -2387,6 +2387,51 @@ first.
 If nonzero, this disables the new 32-bit memory-mapping layout;
 the kernel will use the legacy (2.4) layout for all processes.
 .TP
+.IR /proc/sys/vm/memory_failure_early_kill " (since Linux 2.6.32)"
+.\" The following is based on the text in Documentation/sysctl/vm.txt
+Control how to kill processes when an uncorrected memory error
+(typically a 2-bit error in a memory module)
+that cannot be handled by the kernel
+is detected in the background by hardware.
+In some cases (like the page still having a valid copy on disk),
+the kernel will handle the failure
+transparently without affecting any applications.
+But if there is no other up-to-date copy of the data,
+it will kill processes to prevent any data corruptions from propagating.
+
+The file has one of the following values:
+.RS
+.IP 1: 4
+Kill all processes that have the corrupted-and-not-reloadable page mapped
+as soon as the corruption is detected.
+Note this is not supported for a few types of pages, like kernel internally
+allocated data or the swap cache, but works for the majority of user pages.
+
+.IP 0: 4
+Only unmap the corrupted page from all processes and only kill a process
+who tries to access it.
+.RE
+.IP
+The kill is performed using a
+.B SIGBUS 
+signal with
+.I si_code
+set to
+.BR BUS_MCEERR_AO .
+Processes can handle this if they want to; see
+.BR sigaction (2) 
+for more details.
+
+This feature is only active on architectures/platforms with advanced machine
+check handling and depends on the hardware capabilities.
+
+Applications can override the
+.I memory_failure_early_kill
+setting individually with the
+.BR prctl (2)
+.B PR_MCE_KILL
+operation.
+.TP
 .IR /proc/sys/vm/oom_dump_tasks " (since Linux 2.6.25)"
 .\" The following is from Documentation/sysctl/vm.txt
 Enables a system-wide task dump (excluding kernel threads) to be