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Timer race condition#243

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kilograham merged 1 commit intodevelop-1.1.1from
timer-race-condition
Mar 10, 2021
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Timer race condition#243
kilograham merged 1 commit intodevelop-1.1.1from
timer-race-condition

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@kilograham kilograham commented Mar 8, 2021

fixes #195

@kilograham kilograham force-pushed the timer-race-condition branch from 367eb34 to e2968db Compare March 8, 2021 21:47
@kilograham
hardware_timer: fix race condition whem a new timer being added becom…
1e658f2 
…es missed thus obviating the need for an IRQ but there is an IRQ already pending for another timer
@kilograham kilograham force-pushed the timer-race-condition branch from e2968db to 1e658f2 Compare March 8, 2021 21:49
@kilograham kilograham requested a review from Wren6991 March 8, 2021 21:50
@kilograham kilograham added this to the 1.1.1 milestone Mar 8, 2021
@kilograham kilograham linked an issue Mar 8, 2021 that may be closed by this pull request
Repeated invocation of function "void sleep_us(uint64_t us)" can cause lockup #195
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lurch
lurch reviewed Mar 8, 2021
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Wren6991
Wren6991 approved these changes Mar 10, 2021
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So the failure mode was an alarm firing at the point we were in the critical section setting an immediately-expiring timer on the same alarm, and getting dropped as a result?

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kilograham commented Mar 10, 2021

So the failure mode was an alarm firing at the point we were in the critical section setting an immediately-expiring timer on the same alarm, and getting dropped as a result?

setting an immediately expiring timer when there was already a timer that had fired but not yet been serviced (because we were under lock)

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kilograham commented Mar 10, 2021

note it also requires a mix of timers adding in IRQ (i.e. repeating) and non IRQ contexts (we already had a test which created a huge number of timers with random timeouts and makes sure they all happen and in the right order - just none of those repeated)

@kilograham kilograham merged commit d36b1ca into develop-1.1.1 Mar 10, 2021
@kilograham kilograham deleted the timer-race-condition branch March 10, 2021 18:04
@lurch lurch mentioned this pull request Mar 12, 2021
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Repeated invocation of function "void sleep_us(uint64_t us)" can cause lockup

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