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author | Nathan Lynch <nathanl@linux.ibm.com> | 2021-03-15 03:00:45 -0500 |
---|---|---|
committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-03-23 09:25:12 +1100 |
commit | 274cb1ca2e7ce02cab56f5f4c61a74aeb566f931 (patch) | |
tree | 2d7560711667736ecb0664d10b44be597fdfcece | |
parent | e834df6cfc71d8e5ce2c27a0184145ea125c3f0f (diff) | |
download | linux-stable-274cb1ca2e7ce02cab56f5f4c61a74aeb566f931.tar.gz linux-stable-274cb1ca2e7ce02cab56f5f4c61a74aeb566f931.tar.bz2 linux-stable-274cb1ca2e7ce02cab56f5f4c61a74aeb566f931.zip |
powerpc/pseries/mobility: handle premature return from H_JOIN
The pseries join/suspend sequence in its current form was written with
the assumption that it was the only user of H_PROD and that it needn't
handle spurious successful returns from H_JOIN. That's wrong;
powerpc's paravirt spinlock code uses H_PROD, and CPUs entering
do_join() can be woken prematurely from H_JOIN with a status of
H_SUCCESS as a result. This causes all CPUs to exit the sequence
early, preventing suspend from occurring at all.
Add a 'done' boolean flag to the pseries_suspend_info struct, and have
the waking thread set it before waking the other threads. Threads
which receive H_SUCCESS from H_JOIN retry if the 'done' flag is still
unset.
Fixes: 9327dc0aeef3 ("powerpc/pseries/mobility: use stop_machine for join/suspend")
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210315080045.460331-3-nathanl@linux.ibm.com
-rw-r--r-- | arch/powerpc/platforms/pseries/mobility.c | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/arch/powerpc/platforms/pseries/mobility.c b/arch/powerpc/platforms/pseries/mobility.c index a6739ce9feac..e83e0891272d 100644 --- a/arch/powerpc/platforms/pseries/mobility.c +++ b/arch/powerpc/platforms/pseries/mobility.c @@ -458,9 +458,12 @@ static int do_suspend(void) * or if an error is received from H_JOIN. The thread which performs * the first increment (i.e. sets it to 1) is responsible for * waking the other threads. + * @done: False if join/suspend is in progress. True if the operation is + * complete (successful or not). */ struct pseries_suspend_info { atomic_t counter; + bool done; }; static int do_join(void *arg) @@ -470,6 +473,7 @@ static int do_join(void *arg) long hvrc; int ret; +retry: /* Must ensure MSR.EE off for H_JOIN. */ hard_irq_disable(); hvrc = plpar_hcall_norets(H_JOIN); @@ -485,8 +489,20 @@ static int do_join(void *arg) case H_SUCCESS: /* * The suspend is complete and this cpu has received a - * prod. + * prod, or we've received a stray prod from unrelated + * code (e.g. paravirt spinlocks) and we need to join + * again. + * + * This barrier orders the return from H_JOIN above vs + * the load of info->done. It pairs with the barrier + * in the wakeup/prod path below. */ + smp_mb(); + if (READ_ONCE(info->done) == false) { + pr_info_ratelimited("premature return from H_JOIN on CPU %i, retrying", + smp_processor_id()); + goto retry; + } ret = 0; break; case H_BAD_MODE: @@ -500,6 +516,13 @@ static int do_join(void *arg) if (atomic_inc_return(counter) == 1) { pr_info("CPU %u waking all threads\n", smp_processor_id()); + WRITE_ONCE(info->done, true); + /* + * This barrier orders the store to info->done vs subsequent + * H_PRODs to wake the other CPUs. It pairs with the barrier + * in the H_SUCCESS case above. + */ + smp_mb(); prod_others(); } /* @@ -553,6 +576,7 @@ static int pseries_suspend(u64 handle) info = (struct pseries_suspend_info) { .counter = ATOMIC_INIT(0), + .done = false, }; ret = stop_machine(do_join, &info, cpu_online_mask); |