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Kernel: Instrument syscalls with their process big lock requirements

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Currently all syscalls run under the Process:m_big_lock, which is an
obvious bottleneck. Long term we would like to remove the big lock and
replace it with the required fine grained locking.

To facilitate this goal we need a way of gradually decomposing the big
lock into the all of the required fine grained locks. This commit
introduces instrumentation to the syscall table, allowing the big lock
requirement to be toggled on/off per syscall.

Eventually when we are finished, no syscall will required the big lock,
and we'll be able to remove all of this instrumentation.
This commit is contained in:
Brian Gianforcaro 2021-07-18 09:18:35 -07:00 • committed by Gunnar Beutner
parent 308396bca1
commit af543328ea
3 changed files with 179 additions and 163 deletions
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15
Kernel/Syscall.cpp
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@ -90,8 +90,13 @@ UNMAP_AFTER_INIT void initialize()
#pragma GCC diagnostic ignored "-Wcast-function-type"
typedef KResultOr<FlatPtr> (Process::*Handler)(FlatPtr, FlatPtr, FlatPtr);
typedef KResultOr<FlatPtr> (Process::*HandlerWithRegisterState)(RegisterState&);
#define __ENUMERATE_SYSCALL(x) reinterpret_cast<Handler>(&Process::sys$##x),
static const Handler s_syscall_table[] = {
struct HandlerMetadata {
Handler handler;
NeedsBigProcessLock needs_lock;
};
#define __ENUMERATE_SYSCALL(sys_call, needs_lock) { reinterpret_cast<Handler>(&Process::sys$##sys_call), needs_lock },
static const HandlerMetadata s_syscall_table[] = {
ENUMERATE_SYSCALLS(__ENUMERATE_SYSCALL)
};
#undef __ENUMERATE_SYSCALL
@ -126,7 +131,7 @@ KResultOr<FlatPtr> handle(RegisterState& regs, FlatPtr function, FlatPtr arg1, F
if (function == SC_fork || function == SC_sigreturn) {
// These syscalls want the RegisterState& rather than individual parameters.
auto handler = (HandlerWithRegisterState)s_syscall_table[function];
auto handler = (HandlerWithRegisterState)s_syscall_table[function].handler;
return (process.*(handler))(regs);
}
@ -135,12 +140,12 @@ KResultOr<FlatPtr> handle(RegisterState& regs, FlatPtr function, FlatPtr arg1, F
return ENOSYS;
}
if (s_syscall_table[function] == nullptr) {
if (s_syscall_table[function].handler == nullptr) {
dbgln("Null syscall {} requested, you probably need to rebuild this program!", function);
return ENOSYS;
}
return (process.*(s_syscall_table[function]))(arg1, arg2, arg3);
return (process.*(s_syscall_table[function].handler))(arg1, arg2, arg3);
}
}