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 modification 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 con-
trols that can be modified by the owner of the calling pro-
cess, privileged controls that can be modified only by
privileged callers, and system controls 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 rctlblk_set_value(3C)).
For limits on collective entities such as the task or pro-
ject, the process ID of the calling process is associated
with the resource control 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() (see 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 flag 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.
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() function (see
rctlblk_set_value(3C)). 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 currently 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 rctl with the given name is known to the system.
ENOENT
No value beyond the given resource control block
exists.
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
support the usage operation.
The setrctl() function will fail if:
EACCESS
The rctl value specified cannot be changed by the
current process.
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 <sys/types.h>
#include <rctl.h>
#include <stdio.h>
uint64_t value;
int cur_signal;
rctlblk_t *rblk;
...
if ((rblk = 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",
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. Multiple blocks of
equal value and privilege will likely 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 existing RCPRIV_BASIC value owned by that
process on the control to be deleted.
The resource control facility provides the backend implemen-
tation for both setrctl()/getrctl() and
setrlimit()/getrlimit(). The facility behaves consistently
when either of these interfaces is used exclusively; when
using both interfaces, the caller must be aware of the ord-
ering 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 con-
trols 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 possi-
ble 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 con-
trol 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 attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | Async-Signal-Safe |
|_____________________________|_____________________________|
SEE ALSO
getrlimit(2), errno(3C), rctlblk_set_value(3C), attri-
butes(5)
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