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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-10-30 13:29:40 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2019-10-31 11:09:10 -0300
commit6b1472eb2ea16f99c4729f975ca25af980ce3894 (patch)
tree14cd1db1ac52188e91e81ab3ef3a93735d1683be /sysdeps
parentfbb4a3143724ef3f044a4f05351fe041300ee382 (diff)
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Refactor PI mutexes internal definitions
This patch adds the generic futex_lock_pi and futex_unlock_pi to wrap around the syscall machinery required to issue the syscall calls. It simplifies a bit the futex code required to implement PI mutexes. No function changes, checked on x86_64-linux-gnu. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Diffstat (limited to 'sysdeps')
-rw-r--r--sysdeps/nptl/futex-internal.h86
-rw-r--r--sysdeps/nptl/lowlevellock-futex.h9
2 files changed, 95 insertions, 0 deletions
diff --git a/sysdeps/nptl/futex-internal.h b/sysdeps/nptl/futex-internal.h
index 7692146..4feb772 100644
--- a/sysdeps/nptl/futex-internal.h
+++ b/sysdeps/nptl/futex-internal.h
@@ -381,4 +381,90 @@ futex_wake (unsigned int* futex_word, int processes_to_wake, int private)
}
}
+/* The operation checks the value of the futex, if the value is 0, then
+ it is atomically set to the caller's thread ID. If the futex value is
+ nonzero, it is atomically sets the FUTEX_WAITERS bit, which signals wrt
+ other futex owner that it cannot unlock the futex in user space by
+ atomically by setting its value to 0.
+
+ If more than one wait operations is issued, the enqueueing of the waiters
+ are done in descending priority order.
+
+ The ABSTIME arguments provides an absolute timeout (measured against the
+ CLOCK_REALTIME clock). If TIMEOUT is NULL, the operation will block
+ indefinitely.
+
+ Returns:
+
+ - 0 if woken by a PI unlock operation or spuriously.
+ - EAGAIN if the futex owner thread ID is about to exit, but has not yet
+ handled the state cleanup.
+ - EDEADLK if the futex is already locked by the caller.
+ - ESRCH if the thread ID int he futex does not exist.
+ - EINVAL is the state is corrupted or if there is a waiter on the
+ futex.
+ - ETIMEDOUT if the ABSTIME expires.
+*/
+static __always_inline int
+futex_lock_pi (unsigned int *futex_word, const struct timespec *abstime,
+ int private)
+{
+ int err = lll_futex_timed_lock_pi (futex_word, abstime, private);
+ switch (err)
+ {
+ case 0:
+ case -EAGAIN:
+ case -EINTR:
+ case -ETIMEDOUT:
+ case -ESRCH:
+ case -EDEADLK:
+ case -EINVAL: /* This indicates either state corruption or that the kernel
+ found a waiter on futex address which is waiting via
+ FUTEX_WAIT or FUTEX_WAIT_BITSET. This is reported on
+ some futex_lock_pi usage (pthread_mutex_timedlock for
+ instance). */
+ return -err;
+
+ case -EFAULT: /* Must have been caused by a glibc or application bug. */
+ case -ENOSYS: /* Must have been caused by a glibc bug. */
+ /* No other errors are documented at this time. */
+ default:
+ futex_fatal_error ();
+ }
+}
+
+/* Wakes the top priority waiter that called a futex_lock_pi operation on
+ the futex.
+
+ Returns the same values as futex_lock_pi under those same conditions;
+ additionally, returns EPERM when the caller is not allowed to attach
+ itself to the futex. */
+static __always_inline int
+futex_unlock_pi (unsigned int *futex_word, int private)
+{
+ int err = lll_futex_timed_unlock_pi (futex_word, private);
+ switch (err)
+ {
+ case 0:
+ case -EAGAIN:
+ case -EINTR:
+ case -ETIMEDOUT:
+ case -ESRCH:
+ case -EDEADLK:
+ case -ENOSYS:
+ case -EPERM: /* The caller is not allowed to attach itself to the futex.
+ Used to check if PI futexes are supported by the
+ kernel. */
+ return -err;
+
+ case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+ being normalized. Must have been caused by a glibc or
+ application bug. */
+ case -EFAULT: /* Must have been caused by a glibc or application bug. */
+ /* No other errors are documented at this time. */
+ default:
+ futex_fatal_error ();
+ }
+}
+
#endif /* futex-internal.h */
diff --git a/sysdeps/nptl/lowlevellock-futex.h b/sysdeps/nptl/lowlevellock-futex.h
index 392277e..ff0fd4e 100644
--- a/sysdeps/nptl/lowlevellock-futex.h
+++ b/sysdeps/nptl/lowlevellock-futex.h
@@ -140,6 +140,15 @@
/* Priority Inheritance support. */
+#define lll_futex_timed_lock_pi(futexp, abstime, private) \
+ lll_futex_syscall (4, futexp, \
+ __lll_private_flag (FUTEX_LOCK_PI, private), \
+ 0, abstime)
+
+#define lll_futex_timed_unlock_pi(futexp, private) \
+ lll_futex_syscall (4, futexp, \
+ __lll_private_flag (FUTEX_UNLOCK_PI, private), \
+ 0, 0)
/* Like lll_futex_wait (FUTEXP, VAL, PRIVATE) but with the expectation
that lll_futex_cmp_requeue_pi (FUTEXP, _, _, MUTEX, _, PRIVATE) will