4.4-stable review patch. If anyone has any objections, please let me know.
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From: Qiao Zhou qiaozhou@asrmicro.com
commit 6f44a0bacb79a03972c83759711832b382b1b8ac upstream.
In current die(), the irq is disabled for __die() handle, not including the possible panic() handling. Since the log in __die() can take several hundreds ms, new irq might come and interrupt current die().
If the process calling die() holds some critical resource, and some other process scheduled later also needs it, then it would deadlock. The first panic will not be executed.
So here disable irq for the whole flow of die().
Signed-off-by: Qiao Zhou qiaozhou@asrmicro.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/kernel/traps.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -239,10 +239,12 @@ void die(const char *str, struct pt_regs { struct thread_info *thread = current_thread_info(); int ret; + unsigned long flags; + + raw_spin_lock_irqsave(&die_lock, flags);
oops_enter();
- raw_spin_lock_irq(&die_lock); console_verbose(); bust_spinlocks(1); ret = __die(str, err, thread, regs); @@ -252,13 +254,15 @@ void die(const char *str, struct pt_regs
bust_spinlocks(0); add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE); - raw_spin_unlock_irq(&die_lock); oops_exit();
if (in_interrupt()) panic("Fatal exception in interrupt"); if (panic_on_oops) panic("Fatal exception"); + + raw_spin_unlock_irqrestore(&die_lock, flags); + if (ret != NOTIFY_STOP) do_exit(SIGSEGV); }