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Thread: Set m_blocker to null in Thread::unblock()

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Before this commit, m_blocker was only set to null in Thread::block,
after the thread has been unblocked.

Starting with this commit, m_blocker is also set to null in
Thread::unblock.

This change will allow us to implement a missing feature of the PT_TRACE
command of the ptrace syscall - stopping the traced thread when it
exits the execve syscall.

That feature will be implemented by sending a blocking SIGSTOP to the
traced thread after it has executed the execve logic and before it
starts executing the new program in userspace.

However, since Process::exec arranges the tss to return to userspace
(the so-called "yield-teleport"), the code in Thread::block that should
be run after the thread unblocks, and sets m_blocker to null, never
actually runs.

Setting m_blocker to null in Thread::unblock allows us to avoid an
incorrect state where the thread is in a Running state but conatins a
pointer to a Blocker.
This commit is contained in:
Itamar 2020-04-06 15:38:33 +03:00 • committed by Andreas Kling
parent b306ac9b2b
commit 4568a628f9
Notes: sideshowbarker 2024-07-19 07:39:12 +09:00
1 changed files with 1 additions and 0 deletions
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Kernel/Thread.cpp
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@ -163,6 +163,7 @@ Thread::~Thread()
void Thread::unblock()
{
m_blocker = nullptr;
if (current == this) {
if (m_should_die)
set_state(Thread::Dying);