Re: [PATCH v4 14/15] livepatch: add /proc/<pid>/patch_state
From: Miroslav Benes <mbenes@suse.cz>
Date: 2017-01-31 14:31:56
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linux-s390, lkml
On Thu, 19 Jan 2017, Josh Poimboeuf wrote:
quoted hunk ↗ jump to hunk
Expose the per-task patch state value so users can determine which tasks are holding up completion of a patching operation. Signed-off-by: Josh Poimboeuf <redacted> Reviewed-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Miroslav Benes <mbenes@suse.cz> --- Documentation/filesystems/proc.txt | 18 ++++++++++++++++++ fs/proc/base.c | 15 +++++++++++++++ 2 files changed, 33 insertions(+)diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 72624a1..85c501b 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt@@ -44,6 +44,7 @@ Table of Contents 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 3.9 /proc/<pid>/map_files - Information about memory mapped files 3.10 /proc/<pid>/timerslack_ns - Task timerslack value + 3.11 /proc/<pid>/patch_state - Livepatch patch operation state 4 Configuring procfs 4.1 Mount options@@ -1886,6 +1887,23 @@ Valid values are from 0 - ULLONG_MAX An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level permissions on the task specified to change its timerslack_ns value. +3.11 /proc/<pid>/patch_state - Livepatch patch operation state +----------------------------------------------------------------- +When CONFIG_LIVEPATCH is enabled, this file displays the value of the +patch state for the task. + +A value of '-1' indicates that no patch is in transition. + +A value of '0' indicates that a patch is in transition and the task is +unpatched. If the patch is being enabled, then the task hasn't been +patched yet. If the patch is being disabled, then the task has already +been unpatched. + +A value of '1' indicates that a patch is in transition and the task is +patched. If the patch is being enabled, then the task has already been +patched. If the patch is being disabled, then the task hasn't been +unpatched yet. +
Despite my review I thought about this some more. I think the logic make sense internally but when exposed it can be confusing. We do not export klp_target_state value, so users have to know if a patch is being enabled or disabled. Of course, they should know that, but I guess they'd like to use an userspace tool for this. Such tool needs to look at /proc/<pid>/patch_state to find out which tasks are blocking the completion and that is it. No more information anywhere. We can either export klp_target_state, or change /proc/<pid>/patch_state to show only two states - task is in transition (1), task is patched (0). What do you think? Miroslav