linux-kernel - kernel/posix-timer.c: Forgot to disable interrupts in sys_timer

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Message-ID: <7fcc02550908231518m1d35a0c6kd4397b974ac65747@mail.gmail.com>
Date:	Sun, 23 Aug 2009 17:18:02 -0500
From:	Lin Tan <tammy000@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: kernel/posix-timer.c: Forgot to disable interrupts in 
	sys_timer_settime()?

Hi,

Did we forget to disable interrupts before calling
posix_cpu_timer_set() in the system call function sys_timer_settime()
(in code literally as SYSCALL_DEFINE4(timer_settime, ...) as shown
below)? The CLOCK_DISPATCH macro invokes posix_cpu_timer_set(), which
requires interrupts to be disabled upon entry of calling. When
posix_cpu_timer_set() was called from other functions such as
do_cpu_nanosleep(), interrupts are disabled.

SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
 769                const struct itimerspec __user *, new_setting,
 770                struct itimerspec __user *, old_setting)
 771{
    ...
 792        error = CLOCK_DISPATCH(timr->it_clock, timer_set,
 793                               (timr, flags, &new_spec, rtn)); //
this MACRO invokes posix_cpu_timer_set()
 ...
}

In addition, its block comments also state that we must disable
interrupts before calling it (in posix-cpu-timers.c):

/*
 712 * ...
 713 * This is called with the timer locked and interrupts disabled.
 714 *
 ...
 716 */
 717int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 718                        struct itimerspec *new, struct itimerspec *old)
 719{
  ...
}

Thanks,
Lin
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