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nptl: Add EOVERFLOW checks for futex calls

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Some futex-internal calls require additional check for EOVERFLOW (as
indicated by [1] [2] [3]).  For both mutex and rwlock code, EOVERFLOW is
handle as ETIMEDOUT; since it indicate to the caller that the blocking
operation could not be issued.

For mutex it avoids a possible issue where PTHREAD_MUTEX_ROBUST_* might
assume EOVERFLOW indicate futex has succeed, and for PTHREAD_MUTEX_PP_*
it avoid a potential busy infinite loop.  For rwlock and semaphores, it
also avoids potential busy infinite loops.

Checked on x86_64-linux-gnu and i686-linux-gnu, although EOVERFLOW
won't be possible with current usage (since all timeouts on 32-bit
architectures with 32-bit time_t support will be in the range of
32-bit time_t).

[1] https://sourceware.org/pipermail/libc-alpha/2020-November/120079.html
[2] https://sourceware.org/pipermail/libc-alpha/2020-November/120080.html
[3] https://sourceware.org/pipermail/libc-alpha/2020-November/120127.html
This commit is contained in:
Adhemerval Zanella
2020-11-26 10:54:04 -03:00
parent 71eeae0325
commit aa69f19a93
4 changed files with 13 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
nptl/pthread_rwlock_common.c
View File

@ -334,7 +334,7 @@ __pthread_rwlock_rdlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid,
private);
/* We ignore EAGAIN and EINTR. On time-outs, we can just
return because we don't need to clean up anything. */
if (err == ETIMEDOUT)
if (err == ETIMEDOUT || err == EOVERFLOW)
return err;
}
/* It makes sense to not break out of the outer loop here
@ -460,7 +460,7 @@ __pthread_rwlock_rdlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid,
int err = __futex_abstimed_wait64 (&rwlock->__data.__wrphase_futex,
1 | PTHREAD_RWLOCK_FUTEX_USED,
clockid, abstime, private);
if (err == ETIMEDOUT)
if (err == ETIMEDOUT || err == EOVERFLOW)
{
/* If we timed out, we need to unregister. If no read phase
has been installed while we waited, we can just decrement
@ -479,7 +479,7 @@ __pthread_rwlock_rdlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid,
if (atomic_compare_exchange_weak_relaxed
(&rwlock->__data.__readers, &r,
r - (1 << PTHREAD_RWLOCK_READER_SHIFT)))
return ETIMEDOUT;
return err;
/* TODO Back-off. */
}
/* Use the acquire MO fence to mirror the steps taken in the
@ -730,7 +730,7 @@ __pthread_rwlock_wrlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid,
int err = __futex_abstimed_wait64 (&rwlock->__data.__writers_futex,
1 | PTHREAD_RWLOCK_FUTEX_USED,
clockid, abstime, private);
if (err == ETIMEDOUT)
if (err == ETIMEDOUT || err == EOVERFLOW)
{
if (prefer_writer)
{
@ -758,7 +758,7 @@ __pthread_rwlock_wrlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid,
}
/* We cleaned up and cannot have stolen another waiting writer's
futex wake-up, so just return. */
return ETIMEDOUT;
return err;
}
/* If we got interrupted (EINTR) or the futex word does not have the
expected value (EAGAIN), retry after reloading __readers. */
@ -829,7 +829,7 @@ __pthread_rwlock_wrlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid,
int err = __futex_abstimed_wait64 (&rwlock->__data.__wrphase_futex,
PTHREAD_RWLOCK_FUTEX_USED,
clockid, abstime, private);
if (err == ETIMEDOUT)
if (err == ETIMEDOUT || err == EOVERFLOW)
{
if (rwlock->__data.__flags != PTHREAD_RWLOCK_PREFER_READER_NP)
{
@ -861,7 +861,7 @@ __pthread_rwlock_wrlock_full64 (pthread_rwlock_t *rwlock, clockid_t clockid,
if ((wf & PTHREAD_RWLOCK_FUTEX_USED) != 0)
futex_wake (&rwlock->__data.__writers_futex,
1, private);
return ETIMEDOUT;
return err;
}
/* TODO Back-off. */
}