On 06/15/2015 12:59 PM, Aurelien Jarno wrote:
>> This means glibc-2.20 doesn't support PI/robust mutex on ARM at all,
>> glibc-2.21 needs --enable-kernel=3.14.3.
>
> That's not correct.
I was describing the situation as it is, with an unpatched glibc.
tested on kernel-4.0:
Debian experimental glibc-2.21 --> BAD
glibc-2.20 --enable-kernel-3.0 --> BAD
glibc-2.20 + HACK[1]--enable-kernel-3.0 --> GOOD
glibc-2.21 --enable-kernel-3.0 --> BAD
glibc-2.21 --enable-kernel-3.15 --> GOOD
> The __ASSUME_* defines tells that the feature is
> there unconditionally. When they are not defined, the code should probe
> for the feature before using it, and if it is not present, fallback to
> a compatibility code. I guess there is a bug in the probe or the
> compatibility code, and it's what we want to fix.
Sounds reasonable, I tried to reopen the glibc bug 9894 that caused this
regression but I had no luck
(https://sourceware.org/bugzilla/show_bug.cgi?id=9894#c20)
Marc
[1]
index e755741de60b..a56290ce4ca4 100644
--- a/sysdeps/unix/sysv/linux/arm/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/arm/kernel-features.h
@@ -37,6 +37,6 @@
/* The ARM kernel may or may not support
futex_atomic_cmpxchg_inatomic, depending on kernel
configuration. */
-#undef __ASSUME_FUTEX_LOCK_PI
-#undef __ASSUME_REQUEUE_PI
-#undef __ASSUME_SET_ROBUST_LIST
+//#undef __ASSUME_FUTEX_LOCK_PI
+//#undef __ASSUME_REQUEUE_PI
+//#undef __ASSUME_SET_ROBUST_LIST
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