[jira] [Commented] (STDCXX-1072) [Oracle Solaris/SPARCV8] stricter mutex alignment requirements
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https://issues.apache.org/jira/browse/STDCXX-1072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13473163#comment-13473163
]
Liviu Nicoara commented on STDCXX-1072:
---
The attached patch.2.diff uses the aligned buffer class for a cleaner and
slightly more verbose fix.
[Oracle Solaris/SPARCV8] stricter mutex alignment requirements
--
Key: STDCXX-1072
URL: https://issues.apache.org/jira/browse/STDCXX-1072
Project: C++ Standard Library
Issue Type: Bug
Components: Thread Safety
Affects Versions: 4.2.1, 4.2.x, 4.3.x, 5.0.0
Environment: Oracle Solaris on SPARC V8 (or V9 emulation?) hardware.
Reporter: Liviu Nicoara
Assignee: Liviu Nicoara
Labels: SPARC, Solaris, V8, alignment, mutex
Fix For: 4.2.x, 4.3.x, 5.0.0
Attachments: patch.2.diff, patch.diff
Original Estimate: 4h
Remaining Estimate: 4h
The issue has been reported in STDCXX-1040, then STDCXX-1066. The originator
was apparently an improvement (as a response to CR 6296770:
http://tinyurl.com/8ohjsgl) shipped with KU 137111-01
(http://tinyurl.com/ceet6ec) which requires stricter alignment than the
machine word for userland mutexes.
Quoting here the Fujitsu patch notes (in case it goes away):
{quote}
{noformat}
2) When an application using the mutex lock or rw lock in the way shown below
is executed. (*1, *2) ...
*2) ... example of programming that causes the ... problem.
In the case where the problem occurs
int *ip;
mutex_t *mp;
ip = (int *) malloc(sizeof (int) + sizeof (mutex_t));
mp = (mutex_t *) (ip + 1);
/* The address is used with a modification */
In the case where the problem does not occur -1
mutex_t mp; /* Obtained statically */
In the case where the problem does not occur -2
mutex_t *mp;
mp = (mutex_t *) malloc(sizeof (mutex_t));
/* The address is used without any modifications */
{noformat}
{quote}
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[jira] [Commented] (STDCXX-1072) [Oracle Solaris/SPARCV8] stricter mutex alignment requirements
[
https://issues.apache.org/jira/browse/STDCXX-1072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanelfocusedCommentId=13465554#comment-13465554
]
Liviu Nicoara commented on STDCXX-1072:
---
The kernel patch changed the alignment of the userland mutex objects from a
machine word to a double-word boundary. No changes are required of the users
who use such objects in their programs unless users create mutex objects in
buffers which may not be aligned on a proper boundary. E.g., the following are
safe:
{noformat}
mutex_t lock;
struct S {
char misalign;
mutex_t lock;
};
{noformat}
whereas the following is not:
{noformat}
union {
void* align;
char buf [sizeof mutex_t];
} u;
new (u) mutex_t;
{noformat}
because the alignment requirements for void pointer are less strict than for
mutex_t. A few places in the library use the latter for all sorts of static
objects (mostly local statics).
[Oracle Solaris/SPARCV8] stricter mutex alignment requirements
--
Key: STDCXX-1072
URL: https://issues.apache.org/jira/browse/STDCXX-1072
Project: C++ Standard Library
Issue Type: Bug
Components: Thread Safety
Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0, 4.2.1
Environment: Oracle Solaris on SPARC V8 (or V9 emulation?) hardware.
Reporter: Liviu Nicoara
Labels: SPARC, Solaris, V8, alignment, mutex
Fix For: 4.2.x, 4.3.x, 5.0.0
Original Estimate: 4h
Remaining Estimate: 4h
The issue has been reported in STDCXX-1066. The originator was apparently an
improvement (as a response to CR 6296770: http://tinyurl.com/8ohjsgl) shipped
with KU 137111-01 (http://tinyurl.com/ceet6ec) which requires stricter
alignment than the machine word for userland mutexes.
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