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x86: GEODE: MFGPT: fix a potential race when disabling a timer

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We *really* don't want to be reading MFGPTx_SETUP and writing back those
values.  What we want to be doing is clearing CMP1 and CMP2 unconditionally;
otherwise, we have races where CMP1 and/or CMP2 fire after we've read
MFGPTx_SETUP.  They can also fire between when we've written ~CNTEN to
the register, and when the new register values get copied to the timer's
version of the register.  By clearing both fields, we're okay.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Andres Salomon 2008-02-09 23:24:08 +01:00 committed by Thomas Gleixner
parent f087515c65
commit f54ae69baf
1 changed files with 3 additions and 2 deletions
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5
arch/x86/kernel/mfgpt_32.c
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@ -249,8 +249,9 @@ __setup("mfgpt_irq=", mfgpt_setup);
static void mfgpt_disable_timer(u16 clock)
{
u16 val = geode_mfgpt_read(clock, MFGPT_REG_SETUP);
geode_mfgpt_write(clock, MFGPT_REG_SETUP, val & ~MFGPT_SETUP_CNTEN);
/* avoid races by clearing CMP1 and CMP2 unconditionally */
geode_mfgpt_write(clock, MFGPT_REG_SETUP, (u16) ~MFGPT_SETUP_CNTEN |
MFGPT_SETUP_CMP1 | MFGPT_SETUP_CMP2);
}
static int mfgpt_next_event(unsigned long, struct clock_event_device *);