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Commit f54ae69b authored by Andres Salomon's avatar Andres Salomon Committed by Thomas Gleixner
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x86: GEODE: MFGPT: fix a potential race when disabling a timer 



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: default avatarAndres Salomon <dilinger@debian.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent f087515c

arch/x86/kernel/mfgpt_32.c

+3 −2
Original line number Diff line number Diff line
@@ -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 *);