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Work around pty deadlock.

This commit is contained in:
Jonas 'Sortie' Termansen 2022-11-26 12:32:45 +01:00
parent d222003590
commit 632b3ba422
2 changed files with 19 additions and 2 deletions
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1
kernel/linebuffer.cpp
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@ -50,6 +50,7 @@ LineBuffer::~LineBuffer()
bool LineBuffer::Push(uint32_t unicode)
{
// TODO: An infinite line buffer seems like a bad idea.
// Check if we need to allocate or resize the circular queue.
if ( bufferused == bufferlength )
{

20
kernel/pty.cpp
View File

@ -477,6 +477,8 @@ private:
size_t output_offset;
size_t output_used;
static const size_t output_size = 4096;
// TODO: This is not safe because ^W can produce unbounded output.
static const size_t output_probably_safe = 2048;
uint8_t output[output_size];
int ptynum;
@ -538,6 +540,16 @@ ssize_t PTY::master_write(ioctx_t* ctx, const uint8_t* buf, size_t count)
ScopedLockSignal lock(&termlock);
if ( !lock.IsAcquired() )
return errno = EINTR, -1;
// TODO: Work around deadlock by refusing writes when the buffer is starting
// to be too full. This can block / "deadlock" too if the caller
// didn't try to read the data written by a previous call.
while ( output_probably_safe <= output_used )
{
if ( ctx->dflags & O_NONBLOCK )
return errno = EWOULDBLOCK, -1;
if ( !kthread_cond_wait_signal(&output_ready_cond, &termlock) )
return errno = EINTR, -1;
}
size_t sofar = 0;
while ( sofar < count )
{
@ -550,9 +562,13 @@ ssize_t PTY::master_write(ioctx_t* ctx, const uint8_t* buf, size_t count)
{
if ( Signal::IsPending() )
return sofar ? (ssize_t) sofar : (errno = EINTR, -1);
// TODO: Unfortunately sequences like ^W can cause an unbounded
// number of tty_output data causing a deadlock.
ProcessByte(input[i]);
sofar++;
if ( output_probably_safe <= output_used )
return (ssize_t) sofar;
}
sofar += amount;
}
return (ssize_t) sofar;
}
@ -599,7 +615,7 @@ short PTY::PollMasterEventStatus()
short status = 0;
if ( output_used )
status |= POLLIN | POLLRDNORM;
if ( true /* can always write */ )
if ( output_used < output_probably_safe )
status |= POLLOUT | POLLWRNORM;
return status;
}