yangsong8-a1 opened a new pull request, #21592:
URL: https://github.com/apache/nuttx/pull/21592
## Summary
Protect the pipe buffer with a recursive spinlock instead of the rmutex,
so a signal delivered to a writer no longer breaks the lock. Buffers are
allocated and freed with the pipe unlocked: circbuf_reinit() swaps in a
buffer allocated by the caller, and PIPEIOC_SETSIZE uses it.
The series also adds pipecommon_writev(). By default a writev is a byte
stream as before; PIPEIOC_ATOMICWRITE makes a request land in full or
fail with -EMSGSIZE if it can never fit, so a reader never sees half of
a message written in chunks.
- spinlock.h: add rspin_lock_is_locked() and friends, used by the pipe
code
- libc/misc/circbuf: add circbuf_reinit()
- drivers/pipes: rmutex to rspinlock, PIPEIOC_SETSIZE return value fix,
pipecommon_writev()
## Impact
Pipes and FIFOs. New ioctl PIPEIOC_ATOMICWRITE; the default behavior of
write()/writev() is unchanged.
## Testing
Ubuntu 22.04, gcc 13.1, sim:nsh with CONFIG_PIPES. A test program
resizes a pipe, enables atomic mode, then one thread writes 2000
length-prefixed messages with writev() while the main thread reads them
back; it also writes and reads a FIFO:
```
pipe: SETSIZE(256) ret=0, GETSIZE=256
pipe: ATOMICWRITE(1) ret=0
pipe: atomic writev larger than buffer ret=-1 errno=90
pipe: 2000 writev messages read, broken: 0
fifo: open rd=3 wr=4
fifo: write ret=10 errno=0
fifo: read ret=10 data=hello fifo
```
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