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| author | Ahmed S. Darwish <a.darwish@linutronix.de> | 2020-09-04 17:32:31 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-09-10 11:19:31 +0200 |
| commit | 1909760f5fc3f123e47b4e24e0ccdc0fc8f3f106 (patch) | |
| tree | 1f7dad932b8d63072722041e21c1b4a3315a7a4f /lib/mpi/mpi-div.c | |
| parent | 8117ab508f9c476e0a10b9db7f4818f784cf3176 (diff) | |
seqlock: PREEMPT_RT: Do not starve seqlock_t writers
On PREEMPT_RT, seqlock_t is transformed to a sleeping lock that do not
disable preemption. A seqlock_t reader can thus preempt its write side
section and spin for the enter scheduler tick. If that reader belongs to
a real-time scheduling class, it can spin forever and the kernel will
livelock.
To break this livelock possibility on PREEMPT_RT, implement seqlock_t in
terms of "seqcount_spinlock_t" instead of plain "seqcount_t".
Beside its pure annotational value, this will leverage the existing
seqcount_LOCKNAME_T PREEMPT_RT anti-livelock mechanisms, without adding
any extra code.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200904153231.11994-6-a.darwish@linutronix.de
Diffstat (limited to 'lib/mpi/mpi-div.c')
0 files changed, 0 insertions, 0 deletions