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powerpc: Annotate accesses to ipi message flags 

IPI message flags are observed and consequently consumed in the
smp_ipi_demux_relaxed function, which handles these message sources
until it observes none more arriving. Mark the checked loop guard with
READ_ONCE, to signal to KCSAN that the read is known to be volatile, and
that non-determinism is expected. Mark write for message source in
smp_muxed_ipi_set_message().

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230510033117.1395895-8-rmclure@linux.ibm.com
This commit is contained in:
Rohan McLure 2023-05-10 13:31:13 +10:00 committed by Michael Ellerman
parent b0c5b4f1ee
commit 8608f14b49
1 changed files with 2 additions and 2 deletions
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4
arch/powerpc/kernel/smp.c
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@ -291,7 +291,7 @@ void smp_muxed_ipi_set_message(int cpu, int msg)
* Order previous accesses before accesses in the IPI handler.
*/
smp_mb();
message[msg] = 1;
WRITE_ONCE(message[msg], 1);
}
void smp_muxed_ipi_message_pass(int cpu, int msg)
@ -350,7 +350,7 @@ irqreturn_t smp_ipi_demux_relaxed(void)
if (all & IPI_MESSAGE(PPC_MSG_NMI_IPI))
nmi_ipi_action(0, NULL);
#endif
} while (info->messages);
} while (READ_ONCE(info->messages));
return IRQ_HANDLED;
}