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| author | Oleg Nesterov <oleg@redhat.com> | 2015-07-14 14:26:34 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2022-03-04 14:58:54 +0100 |
| commit | bf9ad37dc8a30cce22ae95d6c2ca6abf8731d305 (patch) | |
| tree | edf1be3cce67320700c09e473e1f40ab93114c84 /kernel/Kconfig.preempt | |
| parent | 0ce055f85335e48bc571114d61a70ae217039362 (diff) | |
| download | linux-bf9ad37dc8a30cce22ae95d6c2ca6abf8731d305.tar.bz2 | |
signal, x86: Delay calling signals in atomic on RT enabled kernels
On x86_64 we must disable preemption before we enable interrupts
for stack faults, int3 and debugging, because the current task is using
a per CPU debug stack defined by the IST. If we schedule out, another task
can come in and use the same stack and cause the stack to be corrupted
and crash the kernel on return.
When CONFIG_PREEMPT_RT is enabled, spinlock_t locks become sleeping, and
one of these is the spin lock used in signal handling.
Some of the debug code (int3) causes do_trap() to send a signal.
This function calls a spinlock_t lock that has been converted to a
sleeping lock. If this happens, the above issues with the corrupted
stack is possible.
Instead of calling the signal right away, for PREEMPT_RT and x86,
the signal information is stored on the stacks task_struct and
TIF_NOTIFY_RESUME is set. Then on exit of the trap, the signal resume
code will send the signal when preemption is enabled.
[ rostedt: Switched from #ifdef CONFIG_PREEMPT_RT to
ARCH_RT_DELAYS_SIGNAL_SEND and added comments to the code. ]
[bigeasy: Add on 32bit as per Yang Shi, minor rewording. ]
[ tglx: Use a config option ]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/Ygq5aBB/qMQw6aP5@linutronix.de
Diffstat (limited to 'kernel/Kconfig.preempt')
| -rw-r--r-- | kernel/Kconfig.preempt | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index ce77f0265660..5644abd5f8a8 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -132,4 +132,14 @@ config SCHED_CORE which is the likely usage by Linux distributions, there should be no measurable impact on performance. - +config ARCH_WANTS_RT_DELAYED_SIGNALS + bool + help + This option is selected by architectures where raising signals + can happen in atomic contexts on PREEMPT_RT enabled kernels. This + option delays raising the signal until the return to user space + loop where it is also delivered. X86 requires this to deliver + signals from trap handlers which run on IST stacks. + +config RT_DELAYED_SIGNALS + def_bool PREEMPT_RT && ARCH_WANTS_RT_DELAYED_SIGNALS |