setrctl(2) System Calls setrctl(2)NAME
setrctl, getrctl - set or get resource control values
SYNOPSIS
#include <rctl.h>
int setrctl(const char *controlname, rctlblk_t *old_blk,
rctlblk_t *new_blk, uint_t flags);
int getrctl(const char *controlname, rctlblk_t *old_blk,
rctlblk_t *new_blk, uint_t flags);
DESCRIPTION
The setrctl() and getrctl() functions provide interfaces for the modi‐
fication and retrieval of resource control (rctl) values on active
entities on the system, such as processes, tasks, or projects. All
resource controls are unsigned 64-bit integers; however, a collection
of flags are defined that modify which rctl value is to be set or
retrieved.
Resource controls are restricted to three levels: basic controls that
can be modified by the owner of the calling process, privileged con‐
trols that can be modified only by privileged callers, and system con‐
trols that are fixed for the duration of the operating system instance.
Setting or retrieving each of these controls is performed by setting
the privilege field of the resource control block to RCTL_BASIC,
RCTL_PRIVILEGED, or RCTL_SYSTEM with rctlblk_set_privilege() (see rctl‐
blk_set_value(3C)).
For limits on collective entities such as the task or project, the
process ID of the calling process is associated with the resource con‐
trol value. This ID is available by using rctlblk_get_recipient_pid()
(see rctlblk_set_value(3C)). These values are visible only to that
process and privileged processes within the collective.
The getrctl() function provides a mechanism for iterating through all
of the established values on a resource control. The iteration is
primed by calling getrctl() with old_blk set to NULL, a valid resource
control block pointer in new_blk, and specifying RCTL_FIRST in the
flags argument. Once a resource control block has been obtained,
repeated calls to getrctl() with RCTL_NEXT in the flags argument and
the obtained control in the old_blk argument will return the next
resource control block in the sequence. The iteration reports the end
of the sequence by failing and setting errno to ENOENT.
The getrctl() function allows the calling process to get the current
usage of a controlled resource using RCTL_USAGE as the flags value. The
current value of the resource usage is placed in the value field of the
resource control block specified by new_blk. This value is obtained
with rctlblk_set_value(3C). All other members of the returned block are
undefined and might be invalid.
The setrctl() function allows the creation, modification, or deletion
of action-value pairs on a given resource control. When passed
RCTL_INSERT as the flags value, setrctl() expects new_blk to contain a
new action-value pair for insertion into the sequence. For RCTL_DELETE,
the block indicated by new_blk is deleted from the sequence. For
RCTL_REPLACE, the block matching old_blk is deleted and replaced by the
block indicated by new_blk. When (flags & RCTL_USE_RECIPIENT_PID) is
non-zero, setrctl() uses the process ID set by rctlblk_set_recipi‐
ent_pid(3C) when selecting the rctl value to insert, delete, or replace
basic rctls. Otherwise, the process ID of the calling process is used.
The kernel maintains a history of which resource control values have
triggered for a particular entity, retrievable from a resource control
block with the rctlblk_get_firing_time(3C) function. The insertion or
deletion of a resource control value at or below the currently enforced
value might cause the currently enforced value to be reset. In the
case of insertion, the newly inserted value becomes the actively
enforced value. All higher values that have previously triggered will
have their firing times zeroed. In the case of deletion of the cur‐
rently enforced value, the next higher value becomes the actively
enforced value.
The various resource control block properties are described on the
rctlblk_set_value(3C) manual page.
Resource controls are inherited from the predecessor process or task.
One of the exec(2) functions can modify the resource controls of a
process by resetting their histories, as noted above for insertion or
deletion operations.
RETURN VALUES
Upon successful completion, the setrctl() and getrctl() functions
return 0. Otherwise they return −1 and set errno to indicate the error.
ERRORS
The setrctl() and getrctl() functions will fail if:
EFAULT The controlname, old_blk, or new_blk argument points to an
illegal address.
EINVAL No resource control with the given name is known to the
system, or the resource control block contains properties
that are not valid for the resource control specified.
RCTL_USE_RECIPIENT_PID was used to set a process scope rctl
and the process ID set by rctlblk_set_recipient_pid(3C)
does not match the process ID of calling process.
ENOENT No value beyond the given resource control block exists.
RCTL_USE_RECIPIENT_PID was used and the process ID set by
rctlblk_set_recipient_pid(3C) does not exist within the
current task, project, or zone, depending on the resource
control name.
ESRCH No value matching the given resource control block was
found for any of RCTL_NEXT, RCTL_DELETE, or RCTL_REPLACE.
ENOTSUPP The resource control requested by RCTL_USAGE does not sup‐
port the usage operation.
The setrctl() function will fail if:
EACCES The rctl value specified cannot be changed by the current
process, including the case where the recipient process ID
does not match the calling process and the calling process is
unprivileged.
EPERM An attempt to set a system limit was attempted.
EXAMPLES
Example 1 Retrieve a rctl value.
Obtain the lowest enforced rctl value on the rctl limiting the number
of LWPs in a task.
#include <rctl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
...
rctlblk_t *rblk;
if ((rblk = (rctlblk_t *)malloc(rctlblk_size())) == NULL) {
(void) fprintf(stderr, "malloc failed: %s\n",
strerror(errno));
exit(1);
}
if (getrctl("task.max-lwps", NULL, rblk, RCTL_FIRST) == -1)
(void) fprintf(stderr, "failed to get rctl: %s\n",
strerror(errno));
else
(void) printf("task.max-lwps = %llu\n",
rctlblk_get_value(rblk));
USAGE
Resource control blocks are matched on the value and privilege fields.
Resource control operations act on the first matching resource control
block. Duplicate resource control blocks are not permitted. Multiple
blocks of equal value and privilege need to be entirely deleted and
reinserted, rather than replaced, to have the correct outcome. Resource
control blocks are sorted such that all blocks with the same value that
lack the RCTL_LOCAL_DENY flag precede those having that flag set.
Only one RCPRIV_BASIC resource control value is permitted per process
per control. Insertion of an RCPRIV_BASIC value will cause any exist‐
ing RCPRIV_BASIC value owned by that process on the control to be
deleted.
The resource control facility provides the backend implementation for
both setrctl()/getrctl() and setrlimit()/getrlimit(). The facility
behaves consistently when either of these interfaces is used exclu‐
sively; when using both interfaces, the caller must be aware of the
ordering issues above, as well as the limit equivalencies described in
the following paragraph.
The hard and soft process limits made available with setrlimit() and
getrlimit() are mapped to the resource controls implementation. (New
process resource controls will not be made available with the rlimit
interface.) Because of the RCTL_INSERT and RCTL_DELETE operations, it
is possible that the set of values defined on a resource control has
more or fewer than the two values defined for an rlimit. In this case,
the soft limit is the lowest priority resource control value with the
RCTL_LOCAL_DENY flag set, and the hard limit is the resource control
value with the lowest priority equal to or exceeding RCPRIV_PRIVILEGED
with the RCTL_LOCAL_DENY flag set. If no identifiable soft limit
exists on the resource control and setrlimit() is called, a new
resource control value is created. If a resource control does not have
the global RCTL_GLOBAL_LOWERABLE property set, its hard limit will not
allow lowering by unprivileged callers.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │Async-Signal-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOrctladm(1M), getrlimit(2), errno(3C), rctlblk_set_value(3C),
attributes(5), resource_controls(5)SunOS 5.10 31 Jan 2007 setrctl(2)