• A
    hrtimer: create a "timer_slack" field in the task struct · 6976675d
    Arjan van de Ven 提交于
    We want to be able to control the default "rounding" that is used by
    select() and poll() and friends. This is a per process property
    (so that we can have a "nice" like program to start certain programs with
    a looser or stricter rounding) that can be set/get via a prctl().
    
    For this purpose, a field called "timer_slack_ns" is added to the task
    struct. In addition, a field called "default_timer_slack"ns" is added
    so that tasks easily can temporarily to a more/less accurate slack and then
    back to the default.
    
    The default value of the slack is set to 50 usec; this is significantly less
    than 2.6.27's average select() and poll() timing error but still allows
    the kernel to group timers somewhat to preserve power behavior. Applications
    and admins can override this via the prctl()
    Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
    6976675d
prctl.h 3.3 KB
#ifndef _LINUX_PRCTL_H
#define _LINUX_PRCTL_H

/* Values to pass as first argument to prctl() */

#define PR_SET_PDEATHSIG  1  /* Second arg is a signal */
#define PR_GET_PDEATHSIG  2  /* Second arg is a ptr to return the signal */

/* Get/set current->mm->dumpable */
#define PR_GET_DUMPABLE   3
#define PR_SET_DUMPABLE   4

/* Get/set unaligned access control bits (if meaningful) */
#define PR_GET_UNALIGN	  5
#define PR_SET_UNALIGN	  6
# define PR_UNALIGN_NOPRINT	1	/* silently fix up unaligned user accesses */
# define PR_UNALIGN_SIGBUS	2	/* generate SIGBUS on unaligned user access */

/* Get/set whether or not to drop capabilities on setuid() away from
 * uid 0 (as per security/commoncap.c) */
#define PR_GET_KEEPCAPS   7
#define PR_SET_KEEPCAPS   8

/* Get/set floating-point emulation control bits (if meaningful) */
#define PR_GET_FPEMU  9
#define PR_SET_FPEMU 10
# define PR_FPEMU_NOPRINT	1	/* silently emulate fp operations accesses */
# define PR_FPEMU_SIGFPE	2	/* don't emulate fp operations, send SIGFPE instead */

/* Get/set floating-point exception mode (if meaningful) */
#define PR_GET_FPEXC	11
#define PR_SET_FPEXC	12
# define PR_FP_EXC_SW_ENABLE	0x80	/* Use FPEXC for FP exception enables */
# define PR_FP_EXC_DIV		0x010000	/* floating point divide by zero */
# define PR_FP_EXC_OVF		0x020000	/* floating point overflow */
# define PR_FP_EXC_UND		0x040000	/* floating point underflow */
# define PR_FP_EXC_RES		0x080000	/* floating point inexact result */
# define PR_FP_EXC_INV		0x100000	/* floating point invalid operation */
# define PR_FP_EXC_DISABLED	0	/* FP exceptions disabled */
# define PR_FP_EXC_NONRECOV	1	/* async non-recoverable exc. mode */
# define PR_FP_EXC_ASYNC	2	/* async recoverable exception mode */
# define PR_FP_EXC_PRECISE	3	/* precise exception mode */

/* Get/set whether we use statistical process timing or accurate timestamp
 * based process timing */
#define PR_GET_TIMING   13
#define PR_SET_TIMING   14
# define PR_TIMING_STATISTICAL  0       /* Normal, traditional,
                                                   statistical process timing */
# define PR_TIMING_TIMESTAMP    1       /* Accurate timestamp based
                                                   process timing */

#define PR_SET_NAME    15		/* Set process name */
#define PR_GET_NAME    16		/* Get process name */

/* Get/set process endian */
#define PR_GET_ENDIAN	19
#define PR_SET_ENDIAN	20
# define PR_ENDIAN_BIG		0
# define PR_ENDIAN_LITTLE	1	/* True little endian mode */
# define PR_ENDIAN_PPC_LITTLE	2	/* "PowerPC" pseudo little endian */

/* Get/set process seccomp mode */
#define PR_GET_SECCOMP	21
#define PR_SET_SECCOMP	22

/* Get/set the capability bounding set (as per security/commoncap.c) */
#define PR_CAPBSET_READ 23
#define PR_CAPBSET_DROP 24

/* Get/set the process' ability to use the timestamp counter instruction */
#define PR_GET_TSC 25
#define PR_SET_TSC 26
# define PR_TSC_ENABLE		1	/* allow the use of the timestamp counter */
# define PR_TSC_SIGSEGV		2	/* throw a SIGSEGV instead of reading the TSC */

/* Get/set securebits (as per security/commoncap.c) */
#define PR_GET_SECUREBITS 27
#define PR_SET_SECUREBITS 28

/*
 * Get/set the timerslack as used by poll/select/nanosleep
 * A value of 0 means "use default"
 */
#define PR_SET_TIMERSLACK 29
#define PR_GET_TIMERSLACK 30

#endif /* _LINUX_PRCTL_H */
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