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Kernel: Fix signal delivery

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When delivering urgent signals to the current thread
we need to check if we should be unblocked, and if not
we need to yield to another process.

We also need to make sure that we suppress context switches
during Process::exec() so that we don't clobber the registers
that it sets up (eip mainly) by a context switch. To be able
to do that we add the concept of a critical section, which are
similar to Process::m_in_irq but different in that they can be
requested at any time. Calls to Scheduler::yield and
Scheduler::donate_to will return instantly without triggering
a context switch, but the processor will then asynchronously
trigger a context switch once the critical section is left.
This commit is contained in:
Tom 2020-07-03 05:19:50 -06:00 • committed by Andreas Kling
parent a308b176ce
commit e373e5f007
12 changed files with 242 additions and 95 deletions
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15
Kernel/Lock.cpp
View file

@ -24,6 +24,7 @@
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/TemporaryChange.h>
#include <Kernel/KSyms.h>
#include <Kernel/Lock.h>
#include <Kernel/Thread.h>
@ -67,6 +68,13 @@ void Lock::lock(Mode mode)
}
timeval* timeout = nullptr;
current_thread->wait_on(m_queue, timeout, &m_lock, m_holder, m_name);
} else if (Processor::current().in_critical()) {
// If we're in a critical section and trying to lock, no context
// switch will happen, so yield.
// The assumption is that if we call this from a critical section
// that we DO want to temporarily leave it
TemporaryChange change(Processor::current().in_critical(), 0u);
Scheduler::yield();
}
}
}
@ -95,6 +103,9 @@ void Lock::unlock()
return;
}
// I don't know *who* is using "m_lock", so just yield.
// The assumption is that if we call this from a critical section
// that we DO want to temporarily leave it
TemporaryChange change(Processor::current().in_critical(), 0u);
Scheduler::yield();
}
}
@ -102,7 +113,7 @@ void Lock::unlock()
bool Lock::force_unlock_if_locked()
{
ASSERT(m_mode != Mode::Shared);
InterruptDisabler disabler;
ScopedCritical critical;
if (m_holder != Thread::current())
return false;
ASSERT(m_times_locked == 1);
@ -116,7 +127,7 @@ bool Lock::force_unlock_if_locked()
void Lock::clear_waiters()
{
ASSERT(m_mode != Mode::Shared);
InterruptDisabler disabler;
ScopedCritical critical;
m_queue.clear();
}