Add _monotonic_np versions of timed wait functions
As a follow up to Ibba98f5d88be1c306d14e9b9366302ecbef6d534, where we
added a work around to convert the CLOCK_REALTIME timeouts to
CLOCK_MONOTONIC for pthread and semaphore timed wait functions, we're
introducing a set of _monotonic_np versions of each of these functions
that wait on CLOCK_MONOTONIC directly.
The primary motivation here is that while the above work around helps
for 3rd party code, it creates a dilemma when implementing new code
that would use these functions: either one implements code with these
functions knowing there is a race condition possible or one avoids
these functions and reinvent their own waiting/signaling mechanisms.
Neither are satisfactory, so we create a third option to use these
Android specific _monotonic_np functions that completely remove the
race condition while keeping the rest of the interface.
Specifically this adds the below functions:
pthread_mutex_timedlock_monotonic_np()
pthread_cond_timedwait_monotonic_np()
pthread_rwlock_timedrdlock_monotonic_np()
pthread_rwlock_timedwrlock_monotonic_np()
sem_timedwait_monotonic_np()
Note that pthread_cond_timedwait_monotonic_np() previously existed and
was removed since it's possible to initialize a condition variable to
use CLOCK_MONOTONIC. It is added back for a mix of reasons,
1) Symmetry with the rest of the functions we're adding
2) libc++ cannot easily take advantage of the new initializer, but
will be able to use this function in order to wait on
std::steady_clock
3) Frankly, it's a better API to specify the clock in the waiter function
than to specify the clock when the condition variable is
initialized.
Bug: 73951740
Test: new unit tests
Change-Id: I23aa5c204e36a194237d41e064c5c8ccaa4204e3
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 65e4802..85c9a58 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -770,7 +770,7 @@
pthread_cond_signal;
pthread_cond_timedwait;
pthread_cond_timedwait_monotonic; # arm x86 mips
- pthread_cond_timedwait_monotonic_np; # arm x86 mips
+ pthread_cond_timedwait_monotonic_np; # introduced-arm=16 introduced-x86=16 introduced-mips=16 introduced-arm64=28 introduced-x64_64=28 introduced-mips64=28
pthread_cond_timedwait_relative_np; # arm x86 mips
pthread_cond_timeout_np; # arm x86 mips
pthread_cond_wait;
@@ -1410,10 +1410,14 @@
pselect64;
pthread_attr_getinheritsched;
pthread_attr_setinheritsched;
+ pthread_mutex_timedlock_monotonic_np;
pthread_mutexattr_getprotocol;
pthread_mutexattr_setprotocol;
+ pthread_rwlock_timedrdlock_monotonic_np;
+ pthread_rwlock_timedwrlock_monotonic_np;
pthread_setschedprio;
pthread_sigmask64;
+ sem_timedwait_monotonic_np;
sethostent;
setnetent;
setprotoent;