An application can use the mere fact of epoll_wait returning an fd
as synchronization with the write on the fd that triggered the notification.
This pattern come up in an internal networking server (b/229276331).
If an fd is added to epoll, setup a link from the fd to the epoll fd
and use it for synchronization as well.
Reviewed By: melver
Differential Revision: https://reviews.llvm.org/D124518
The false positive fixed by commit f831d6fc80
("tsan: fix false positive during fd close") still happens episodically
on the added more stressful test which does just open/close.
I don't have a coherent explanation as to what exactly happens
but the fix fixes the false positive on this test as well.
The issue may be related to lost writes during asynchronous MADV_DONTNEED.
I've debugged similar unexplainable false positive related to freed and
reused memory and at the time the only possible explanation I found is that
an asynchronous MADV_DONTNEED may lead to lost writes. That's why commit
302ec7b9bc ("tsan: add memory_limit_mb flag") added StopTheWorld around
the memory flush, but unfortunately the commit does not capture these findings.
Reviewed By: melver
Differential Revision: https://reviews.llvm.org/D121363
FdClose is a subjet to the same atomicity problem as MemoryRangeFreed
(memory state is not "monotoic" wrt race detection).
So we need to lock the thread slot in FdClose the same way we do
in MemoryRangeFreed.
This fixes the modified stress.cpp test.
Reviewed By: vitalybuka, melver
Differential Revision: https://reviews.llvm.org/D121143
If we miss both close of a file descriptor and a subsequent open
if the same file descriptor number, we report false positives
between operations on the old and on the new descriptors.
There are lots of ways to create new file descriptors, but for closing
there is mostly close call. So we try to handle at least it.
However, if the close happens in an ignored library, we miss it
and start reporting false positives.
Handle closing of file descriptors always, even in ignored libraries
(as we do for malloc/free and other critical functions).
But don't imitate memory accesses on close for ignored libraries.
FdClose checks validity of the fd (fd >= 0) itself,
so remove the excessive checks in the callers.
Reviewed By: melver
Differential Revision: https://reviews.llvm.org/D116095
Currently we have MemoryAccess function that accepts
"bool kAccessIsWrite, bool kIsAtomic" and 4 wrappers:
MemoryRead/MemoryWrite/MemoryReadAtomic/MemoryWriteAtomic.
Such scheme with bool flags is not particularly scalable/extendable.
Because of that we did not have Read/Write wrappers for UnalignedMemoryAccess,
and "true, false" or "false, true" at call sites is not very readable.
Moreover, the new tsan runtime will introduce more flags
(e.g. move "freed" and "vptr access" to memory acccess flags).
We can't have 16 wrappers and each flag also takes whole
64-bit register for non-inlined calls.
Introduce AccessType enum that contains bit mask of
read/write, atomic/non-atomic, and later free/non-free,
vptr/non-vptr.
Such scheme is more scalable, more readble, more efficient
(don't consume multiple registers for these flags during calls)
and allows to cover unaligned and range variations of memory
access functions as well.
Also switch from size log to just size.
The new tsan runtime won't have the limitation of supporting
only 1/2/4/8 access sizes, so we don't need the logarithms.
Also add an inline thunk that converts the new interface to the old one.
For inlined calls it should not add any overhead because
all flags/size can be computed as compile time.
Reviewed By: vitalybuka, melver
Differential Revision: https://reviews.llvm.org/D107276
Currently we inconsistently use u32 and int for thread ids,
there are also "unique tid" and "os tid" and just lots of other
things identified by integers.
Additionally new tsan runtime will introduce yet another
thread identifier that is very different from current tids.
Similarly for stack IDs, it's easy to confuse u32 with other
integer identifiers. And when a function accepts u32 or a struct
contains u32 field, it's not always clear what it is.
Add Tid and StackID typedefs to make it clear what is what.
Reviewed By: melver
Differential Revision: https://reviews.llvm.org/D107152
