2e44aea...
by
Benjamin Marzinski via lttng-dev <email address hidden>
fix: handle EINTR correctly in get_cpu_mask_from_sysfs
If the read() in get_cpu_mask_from_sysfs() fails with EINTR, the code is
supposed to retry, but the while loop condition has (bytes_read > 0),
which is false when read() fails with EINTR. The result is that the code
exits the loop, having only read part of the string.
Use (bytes_read != 0) in the while loop condition instead, since the
(bytes_read < 0) case is already handled in the loop.
Older versions of GNU as do not support mftbl. The issue affects Darwin
PowerPC, as well as some older versions of NetBSD and Linux. Since mftb
is equivalent and universally understood, just use that.
The calloc prototype is:
```
void *calloc(size_t nmemb, size_t size);
```
So, just swap the number of members and size arguments to match the prototype, as
we're initialising 1 struct of size `sizeof(struct ...)`. GCC then sees we're not
doing anything wrong.
Signed-off-by: Sam James <email address hidden>
Signed-off-by: Mathieu Desnoyers <email address hidden>
Change-Id: Id84ce5cf9a1b97bfa942597aa188ef6e27e7c10d
Implementations of some atomic operations of GCC for RISC-V are
insufficient for sequential consistency. For this reason Userspace RCU
is currently marked as `broken' for RISC-V with GCC. However, it is
still possible to use other toolchains.
For now, we mark every version of GCC as unsupported. Distribution
package maintainers will have to cherry-pick the relevant patches in GCC
then remove the #error in Userspace RCU if they want to support it.
As for us, we will incrementally add specific versions of GCC that have
fixed the issue whenever new stable releases are made from the GCC
project.
c1c83cc...
by
=?utf-8?q?J=C3=A9r=C3=A9mie_Galarneau?= <email address hidden>
Fix: urcu-bp: misaligned reader accesses
This is a port from a fix in LTTng-UST's embedded urcu (d1a0fad8). The
original message follows:
Running the LTTng-tools tests (test_valid_filter, for example) under
address sanitizer results in the following warning:
/usr/include/lttng/urcu/static/urcu-ust.h:155:6: runtime error: member access within misaligned address 0x7fc45db3a020 for type 'struct lttng_ust_urcu_reader', which requires 128 byte alignment
0x7fc45db3a020: note: pointer points here
c4 7f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ^
While the node member of lttng_ust_urcu_reader has an "aligned"
attribute of CAA_CACHE_LINE_SIZE, the compiler can't ensure the
alignment of members for dynamically allocated instances.
The `data` pointer is changed from char* to struct
lttng_ust_urcu_reader*, allowing the compiler to enforce the expected
alignment constraints.
Since `data` was addressed in bytes, the code using this field is
adapted to use element counts. As the chunks are only used to allocate
reader instances (and not other types), it makes the code a bit easier
to read.
Section 2.2.7 "Atomic Memory Access Instructions" only lists atomic
operations for 32-bit and 64-bit integers. As detailed in Section
2.2.7.1, LL/SC instructions operating on 32-bit and 64-bit integers are
also available. Those are used by the compiler to support atomics on
byte and short types.
This means atomics on 32-bit and 64-bit types have stronger forward
progress guarantees than those operating on 8-bit and 16-bit types.
