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Diffstat (limited to 'hurd/hurdlock.c')
| -rw-r--r-- | hurd/hurdlock.c | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/hurd/hurdlock.c b/hurd/hurdlock.c new file mode 100644 index 0000000000..c06b03cf30 --- /dev/null +++ b/hurd/hurdlock.c @@ -0,0 +1,215 @@ +/* Hurd helpers for lowlevellocks. + Copyright (C) 1999-2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include "hurdlock.h" +#include <hurd.h> +#include <hurd/hurd.h> +#include <time.h> +#include <errno.h> +#include <unistd.h> + +/* Convert an absolute timeout in nanoseconds to a relative + timeout in milliseconds. */ +static inline int __attribute__ ((gnu_inline)) +compute_reltime (const struct timespec *abstime, clockid_t clk) +{ + struct timespec ts; + __clock_gettime (clk, &ts); + + ts.tv_sec = abstime->tv_sec - ts.tv_sec; + ts.tv_nsec = abstime->tv_nsec - ts.tv_nsec; + + if (ts.tv_nsec < 0) + { + --ts.tv_sec; + ts.tv_nsec += 1000000000; + } + + return (ts.tv_sec < 0 ? -1 : + (int)(ts.tv_sec * 1000 + ts.tv_nsec / 1000000)); +} + +int __lll_abstimed_wait (void *ptr, int val, + const struct timespec *tsp, int flags, int clk) +{ + int mlsec = compute_reltime (tsp, clk); + return (mlsec < 0 ? KERN_TIMEDOUT : + lll_timed_wait (ptr, val, mlsec, flags)); +} + +int __lll_abstimed_xwait (void *ptr, int lo, int hi, + const struct timespec *tsp, int flags, int clk) +{ + int mlsec = compute_reltime (tsp, clk); + return (mlsec < 0 ? KERN_TIMEDOUT : + lll_timed_xwait (ptr, lo, hi, mlsec, flags)); +} + +int __lll_abstimed_lock (void *ptr, + const struct timespec *tsp, int flags, int clk) +{ + if (lll_trylock (ptr) == 0) + return (0); + + while (1) + { + if (atomic_exchange_acq ((int *)ptr, 2) == 0) + return (0); + else if (tsp->tv_nsec < 0 || tsp->tv_nsec >= 1000000000) + return (EINVAL); + + int mlsec = compute_reltime (tsp, clk); + if (mlsec < 0 || lll_timed_wait (ptr, + 2, mlsec, flags) == KERN_TIMEDOUT) + return (ETIMEDOUT); + } +} + +/* Robust locks. */ + +/* Test if a given process id is still valid. */ +static inline int valid_pid (int pid) +{ + task_t task = __pid2task (pid); + if (task == MACH_PORT_NULL) + return (0); + + __mach_port_deallocate (__mach_task_self (), task); + return (1); +} + +/* Robust locks have currently no support from the kernel; they + are simply implemented with periodic polling. When sleeping, the + maximum blocking time is determined by this constant. */ +#define MAX_WAIT_TIME 1500 + +int __lll_robust_lock (void *ptr, int flags) +{ + int *iptr = (int *)ptr; + int id = __getpid (); + int wait_time = 25; + unsigned int val; + + /* Try to set the lock word to our PID if it's clear. Otherwise, + mark it as having waiters. */ + while (1) + { + val = *iptr; + if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0) + return (0); + else if (atomic_compare_and_exchange_bool_acq (iptr, + val | LLL_WAITERS, val) == 0) + break; + } + + for (id |= LLL_WAITERS ; ; ) + { + val = *iptr; + if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0) + return (0); + else if (val && !valid_pid (val & LLL_OWNER_MASK)) + { + if (atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0) + return (EOWNERDEAD); + } + else + { + lll_timed_wait (iptr, val, wait_time, flags); + if (wait_time < MAX_WAIT_TIME) + wait_time <<= 1; + } + } +} + +int __lll_robust_abstimed_lock (void *ptr, + const struct timespec *tsp, int flags, int clk) +{ + int *iptr = (int *)ptr; + int id = __getpid (); + int wait_time = 25; + unsigned int val; + + while (1) + { + val = *iptr; + if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0) + return (0); + else if (atomic_compare_and_exchange_bool_acq (iptr, + val | LLL_WAITERS, val) == 0) + break; + } + + for (id |= LLL_WAITERS ; ; ) + { + val = *iptr; + if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0) + return (0); + else if (val && !valid_pid (val & LLL_OWNER_MASK)) + { + if (atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0) + return (EOWNERDEAD); + } + else + { + int mlsec = compute_reltime (tsp, clk); + if (mlsec < 0) + return (ETIMEDOUT); + else if (mlsec > wait_time) + mlsec = wait_time; + + int res = lll_timed_wait (iptr, val, mlsec, flags); + if (res == KERN_TIMEDOUT) + return (ETIMEDOUT); + else if (wait_time < MAX_WAIT_TIME) + wait_time <<= 1; + } + } +} + +int __lll_robust_trylock (void *ptr) +{ + int *iptr = (int *)ptr; + int id = __getpid (); + unsigned int val = *iptr; + + if (!val) + { + if (atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0) + return (0); + } + else if (!valid_pid (val & LLL_OWNER_MASK) && + atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0) + return (EOWNERDEAD); + + return (EBUSY); +} + +void __lll_robust_unlock (void *ptr, int flags) +{ + unsigned int val = atomic_load_relaxed((unsigned int *)ptr); + while (1) + { + if (val & LLL_WAITERS) + { + lll_set_wake (ptr, 0, flags); + break; + } + else if (atomic_compare_exchange_weak_release ((unsigned int *)ptr, &val, 0)) + break; + } +} |